From ce0d53b277d99957de718c16fb923ad36516e251 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 1 Feb 2024 21:29:00 -0500
Subject: [PATCH 01/20] Clean up SampleSource's getters.

---
 Components/6560/6560.hpp                      |   2 +-
 Components/AY38910/AY38910.hpp                |   4 +-
 Components/KonamiSCC/KonamiSCC.hpp            |   2 +-
 Components/OPx/OPLL.hpp                       |   2 +-
 Components/SN76489/SN76489.hpp                |   2 +-
 Machines/Apple/Macintosh/Audio.hpp            |   2 +-
 Machines/Atari/2600/TIASound.hpp              |   2 +-
 Machines/Electron/SoundGenerator.hpp          |   2 +-
 Machines/Enterprise/Dave.hpp                  |   2 +-
 .../Speaker/Implementation/CompoundSource.hpp | 125 +++++++++---------
 .../Speaker/Implementation/LowpassSpeaker.hpp |   8 +-
 .../Speaker/Implementation/SampleSource.hpp   |   4 +-
 12 files changed, 77 insertions(+), 80 deletions(-)

diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index f8c570924..5a55317eb 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -28,7 +28,7 @@ class AudioGenerator: public ::Outputs::Speaker::SampleSource {
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		void skip_samples(std::size_t number_of_samples);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool get_is_stereo() { return false; }
+		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index eee96c093..90c5c9b1f 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -66,7 +66,7 @@ enum class Personality {
 
 	This AY has an attached mono or stereo mixer.
 */
-template <bool is_stereo> class AY38910: public ::Outputs::Speaker::SampleSource {
+template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource {
 	public:
 		/// Creates a new AY38910.
 		AY38910(Personality, Concurrency::AsyncTaskQueue<false> &);
@@ -109,7 +109,7 @@ template <bool is_stereo> class AY38910: public ::Outputs::Speaker::SampleSource
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool get_is_stereo() { return is_stereo; }
+		static constexpr bool is_stereo = stereo;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &task_queue_;
diff --git a/Components/KonamiSCC/KonamiSCC.hpp b/Components/KonamiSCC/KonamiSCC.hpp
index 9b16e8a1d..a0cb3ca30 100644
--- a/Components/KonamiSCC/KonamiSCC.hpp
+++ b/Components/KonamiSCC/KonamiSCC.hpp
@@ -31,7 +31,7 @@ class SCC: public ::Outputs::Speaker::SampleSource {
 		/// As per ::SampleSource; provides audio output.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool get_is_stereo() { return false; }
+		static constexpr bool is_stereo = false;
 
 		/// Writes to the SCC.
 		void write(uint16_t address, uint8_t value);
diff --git a/Components/OPx/OPLL.hpp b/Components/OPx/OPLL.hpp
index 36bb0b51d..284c9ade9 100644
--- a/Components/OPx/OPLL.hpp
+++ b/Components/OPx/OPLL.hpp
@@ -30,7 +30,7 @@ class OPLL: public OPLBase<OPLL> {
 
 		// The OPLL is generally 'half' as loud as it's told to be. This won't strictly be true in
 		// rhythm mode, but it's correct for melodic output.
-		double get_average_output_peak() const { return 0.5; }
+		double average_output_peak() const { return 0.5; }
 
 		/// Reads from the OPL.
 		uint8_t read(uint16_t address);
diff --git a/Components/SN76489/SN76489.hpp b/Components/SN76489/SN76489.hpp
index d419692f8..d720ee256 100644
--- a/Components/SN76489/SN76489.hpp
+++ b/Components/SN76489/SN76489.hpp
@@ -31,7 +31,7 @@ class SN76489: public Outputs::Speaker::SampleSource {
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool get_is_stereo() { return false; }
+		static constexpr bool is_stereo = false;
 
 	private:
 		int master_divider_ = 0;
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index e132015e0..3eabbc832 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -53,7 +53,7 @@ class Audio: public ::Outputs::Speaker::SampleSource {
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
-		constexpr static bool get_is_stereo() { return false; }
+		constexpr static bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &task_queue_;
diff --git a/Machines/Atari/2600/TIASound.hpp b/Machines/Atari/2600/TIASound.hpp
index 67976be58..097b70f52 100644
--- a/Machines/Atari/2600/TIASound.hpp
+++ b/Machines/Atari/2600/TIASound.hpp
@@ -28,7 +28,7 @@ class TIASound: public Outputs::Speaker::SampleSource {
 		// To satisfy ::SampleSource.
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool get_is_stereo() { return false; }
+		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Machines/Electron/SoundGenerator.hpp b/Machines/Electron/SoundGenerator.hpp
index 32cd04074..2429bb37b 100644
--- a/Machines/Electron/SoundGenerator.hpp
+++ b/Machines/Electron/SoundGenerator.hpp
@@ -27,7 +27,7 @@ class SoundGenerator: public ::Outputs::Speaker::SampleSource {
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		void skip_samples(std::size_t number_of_samples);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool get_is_stereo() { return false; }
+		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index 21c08cfe8..7b32f8db1 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -37,7 +37,7 @@ class Audio: public Outputs::Speaker::SampleSource {
 
 		// MARK: - SampleSource.
 		void set_sample_volume_range(int16_t range);
-		static constexpr bool get_is_stereo() { return true; }	// Dave produces stereo sound.
+		static constexpr bool is_stereo = true;
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 
 	private:
diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 75f798e55..52a0a3e71 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -22,62 +22,7 @@ namespace Outputs::Speaker {
 */
 template <typename... T> class CompoundSource:
 	public Outputs::Speaker::SampleSource {
-	public:
-		CompoundSource(T &... sources) : source_holder_(sources...) {
-			// Default: give all sources equal volume.
-			const auto volume = 1.0 / double(source_holder_.size());
-			for(std::size_t c = 0; c < source_holder_.size(); ++c) {
-				volumes_.push_back(volume);
-			}
-		}
-
-		void get_samples(std::size_t number_of_samples, std::int16_t *target) {
-			source_holder_.template get_samples<get_is_stereo()>(number_of_samples, target);
-		}
-
-		void skip_samples(const std::size_t number_of_samples) {
-			source_holder_.skip_samples(number_of_samples);
-		}
-
-		/*!
-			Sets the total output volume of this CompoundSource.
-		*/
-		void set_sample_volume_range(int16_t range) {
-			volume_range_ = range;
-			push_volumes();
-		}
-
-		/*!
-			Sets the relative volumes of the various sources underlying this
-			compound. The caller should ensure that the number of items supplied
-			matches the number of sources and that the values in it sum to 1.0.
-		*/
-		void set_relative_volumes(const std::vector<double> &volumes) {
-			assert(volumes.size() == source_holder_.size());
-			volumes_ = volumes;
-			push_volumes();
-			average_output_peak_ = 1.0 / source_holder_.total_scale(volumes_.data());
-		}
-
-		/*!
-			@returns true if any of the sources owned by this CompoundSource is stereo.
-		*/
-		static constexpr bool get_is_stereo() { return CompoundSourceHolder<T...>::get_is_stereo(); }
-
-		/*!
-			@returns the average output peak given the sources owned by this CompoundSource and the
-				current relative volumes.
-		*/
-		double get_average_output_peak() const {
-			return average_output_peak_;
-		}
-
 	private:
-		void push_volumes() {
-			const double scale = source_holder_.total_scale(volumes_.data());
-			source_holder_.set_scaled_volume_range(volume_range_, volumes_.data(), scale);
-		}
-
 		template <typename... S> class CompoundSourceHolder: public Outputs::Speaker::SampleSource {
 			public:
 				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
@@ -90,9 +35,7 @@ template <typename... T> class CompoundSource:
 					return 0;
 				}
 
-				static constexpr bool get_is_stereo() {
-					return false;
-				}
+				static constexpr bool is_stereo = false;
 
 				double total_scale(double *) const {
 					return 0.0;
@@ -121,7 +64,7 @@ template <typename... T> class CompoundSource:
 
 					// Merge it in; furthermore if total output is stereo but this source isn't,
 					// map it to stereo.
-					if constexpr (output_stereo == S::get_is_stereo()) {
+					if constexpr (output_stereo == S::is_stereo) {
 						while(buffer_size--) {
 							target[buffer_size] += local_samples[buffer_size];
 						}
@@ -144,7 +87,7 @@ template <typename... T> class CompoundSource:
 				}
 
 				void set_scaled_volume_range(int16_t range, double *volumes, double scale) {
-					const auto scaled_range = volumes[0] / double(source_.get_average_output_peak()) * double(range) / scale;
+					const auto scaled_range = volumes[0] / double(source_.average_output_peak()) * double(range) / scale;
 					source_.set_sample_volume_range(int16_t(scaled_range));
 					next_source_.set_scaled_volume_range(range, &volumes[1], scale);
 				}
@@ -153,12 +96,10 @@ template <typename... T> class CompoundSource:
 					return 1 + CompoundSourceHolder<R...>::size();
 				}
 
-				static constexpr bool get_is_stereo() {
-					return S::get_is_stereo() || CompoundSourceHolder<R...>::get_is_stereo();
-				}
+				static constexpr bool is_stereo =  S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
 
 				double total_scale(double *volumes) const {
-					return (volumes[0] / source_.get_average_output_peak()) + next_source_.total_scale(&volumes[1]);
+					return (volumes[0] / source_.average_output_peak()) + next_source_.total_scale(&volumes[1]);
 				}
 
 			private:
@@ -166,6 +107,62 @@ template <typename... T> class CompoundSource:
 				CompoundSourceHolder<R...> next_source_;
 		};
 
+	public:
+		CompoundSource(T &... sources) : source_holder_(sources...) {
+			// Default: give all sources equal volume.
+			const auto volume = 1.0 / double(source_holder_.size());
+			for(std::size_t c = 0; c < source_holder_.size(); ++c) {
+				volumes_.push_back(volume);
+			}
+		}
+
+		void get_samples(std::size_t number_of_samples, std::int16_t *target) {
+			source_holder_.template get_samples<is_stereo>(number_of_samples, target);
+		}
+
+		void skip_samples(const std::size_t number_of_samples) {
+			source_holder_.skip_samples(number_of_samples);
+		}
+
+		/*!
+			Sets the total output volume of this CompoundSource.
+		*/
+		void set_sample_volume_range(int16_t range) {
+			volume_range_ = range;
+			push_volumes();
+		}
+
+		/*!
+			Sets the relative volumes of the various sources underlying this
+			compound. The caller should ensure that the number of items supplied
+			matches the number of sources and that the values in it sum to 1.0.
+		*/
+		void set_relative_volumes(const std::vector<double> &volumes) {
+			assert(volumes.size() == source_holder_.size());
+			volumes_ = volumes;
+			push_volumes();
+			average_output_peak_ = 1.0 / source_holder_.total_scale(volumes_.data());
+		}
+
+		/*!
+			@c true if any of the sources owned by this CompoundSource is stereo.
+		*/
+		static constexpr bool is_stereo = CompoundSourceHolder<T...>::is_stereo;
+
+		/*!
+			@returns the average output peak given the sources owned by this CompoundSource and the
+				current relative volumes.
+		*/
+		double average_output_peak() const {
+			return average_output_peak_;
+		}
+
+	private:
+		void push_volumes() {
+			const double scale = source_holder_.total_scale(volumes_.data());
+			source_holder_.set_scaled_volume_range(volume_range_, volumes_.data(), scale);
+		}
+
 		CompoundSourceHolder<T...> source_holder_;
 		std::vector<double> volumes_;
 		int16_t volume_range_ = 0;
diff --git a/Outputs/Speaker/Implementation/LowpassSpeaker.hpp b/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
index 294e19589..3b64dfcc6 100644
--- a/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
+++ b/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
@@ -348,7 +348,7 @@ template <bool is_stereo> class PushLowpass: public LowpassBase<PushLowpass<is_s
 	source of a high-frequency stream of audio which it filters down to a
 	lower-frequency output.
 */
-template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpass<SampleSource>, SampleSource::get_is_stereo()> {
+template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpass<SampleSource>, SampleSource::is_stereo> {
 	public:
 		PullLowpass(SampleSource &sample_source) : sample_source_(sample_source) {
 			// Propagate an initial volume level.
@@ -362,7 +362,7 @@ template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpa
 		}
 
 		bool get_is_stereo() final {
-			return SampleSource::get_is_stereo();
+			return SampleSource::is_stereo;
 		}
 
 		/*!
@@ -381,7 +381,7 @@ template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpa
 		}
 
 	private:
-		using BaseT = LowpassBase<PullLowpass<SampleSource>, SampleSource::get_is_stereo()>;
+		using BaseT = LowpassBase<PullLowpass<SampleSource>, SampleSource::is_stereo>;
 		friend BaseT;
 		using BaseT::process;
 
@@ -400,7 +400,7 @@ template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpa
 		}
 
 		int get_scale() {
-			return int(65536.0 / sample_source_.get_average_output_peak());
+			return int(65536.0 / sample_source_.average_output_peak());
 		}
 
 		void get_samples(size_t length, int16_t *target) {
diff --git a/Outputs/Speaker/Implementation/SampleSource.hpp b/Outputs/Speaker/Implementation/SampleSource.hpp
index 55e26b221..f9991e7ee 100644
--- a/Outputs/Speaker/Implementation/SampleSource.hpp
+++ b/Outputs/Speaker/Implementation/SampleSource.hpp
@@ -54,7 +54,7 @@ class SampleSource {
 		/*!
 			Indicates whether this component will write stereo samples.
 		*/
-		static constexpr bool get_is_stereo() { return false; }
+		static constexpr bool is_stereo = false;
 
 		/*!
 			Permits a sample source to declare that, averaged over time, it will use only
@@ -66,7 +66,7 @@ class SampleSource {
 			used by a speaker. If it varies, it should do so very infrequently and only to
 			represent changes in hardware configuration.
 		*/
-		double get_average_output_peak() const { return 1.0; }
+		double average_output_peak() const { return 1.0; }
 };
 
 }

From fd73c24fc34d1306a538070798d7492de3479013 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 1 Feb 2024 21:32:16 -0500
Subject: [PATCH 02/20] Use `std::fill`; update volume with slider.

---
 Components/AudioToggle/AudioToggle.cpp | 8 +++++---
 Components/AudioToggle/AudioToggle.hpp | 1 +
 2 files changed, 6 insertions(+), 3 deletions(-)

diff --git a/Components/AudioToggle/AudioToggle.cpp b/Components/AudioToggle/AudioToggle.cpp
index 7188badd9..ee8e2b417 100644
--- a/Components/AudioToggle/AudioToggle.cpp
+++ b/Components/AudioToggle/AudioToggle.cpp
@@ -8,19 +8,20 @@
 
 #include "AudioToggle.hpp"
 
+#include <algorithm>
+
 using namespace Audio;
 
 Audio::Toggle::Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue) :
 	audio_queue_(audio_queue) {}
 
 void Toggle::get_samples(std::size_t number_of_samples, std::int16_t *target) {
-	for(std::size_t sample = 0; sample < number_of_samples; ++sample) {
-		target[sample] = level_;
-	}
+	std::fill(target, target + number_of_samples, level_);
 }
 
 void Toggle::set_sample_volume_range(std::int16_t range) {
 	volume_ = range;
+	level_ = level_active_ ? volume_ : 0;
 }
 
 void Toggle::skip_samples(std::size_t) {}
@@ -29,6 +30,7 @@ void Toggle::set_output(bool enabled) {
 	if(is_enabled_ == enabled) return;
 	is_enabled_ = enabled;
 	audio_queue_.enqueue([this, enabled] {
+		level_active_ = enabled;
 		level_ = enabled ? volume_ : 0;
 	});
 }
diff --git a/Components/AudioToggle/AudioToggle.hpp b/Components/AudioToggle/AudioToggle.hpp
index 8209b4653..defd7a976 100644
--- a/Components/AudioToggle/AudioToggle.hpp
+++ b/Components/AudioToggle/AudioToggle.hpp
@@ -34,6 +34,7 @@ class Toggle: public Outputs::Speaker::SampleSource {
 
 		// Accessed on the audio thread.
 		int16_t level_ = 0, volume_ = 0;
+		bool level_active_ = false;
 };
 
 }

From c6c9be0b08be981f4be7fdc1d31f95c8f223d1b9 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 1 Feb 2024 21:47:44 -0500
Subject: [PATCH 03/20] Adopt CRTP for SampleSource.

---
 Components/6560/6560.hpp                          | 2 +-
 Components/AY38910/AY38910.hpp                    | 2 +-
 Components/AudioToggle/AudioToggle.hpp            | 3 ++-
 Components/KonamiSCC/KonamiSCC.hpp                | 2 +-
 Components/OPx/Implementation/OPLBase.hpp         | 2 +-
 Components/OPx/OPLL.hpp                           | 1 +
 Components/SN76489/SN76489.hpp                    | 2 +-
 Machines/Apple/AppleIIgs/Sound.hpp                | 3 ++-
 Machines/Apple/Macintosh/Audio.hpp                | 2 +-
 Machines/Atari/2600/TIASound.hpp                  | 2 +-
 Machines/Electron/SoundGenerator.hpp              | 2 +-
 Machines/Enterprise/Dave.hpp                      | 2 +-
 Outputs/Speaker/Implementation/CompoundSource.hpp | 4 ++--
 Outputs/Speaker/Implementation/SampleSource.hpp   | 8 +++++++-
 14 files changed, 23 insertions(+), 14 deletions(-)

diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index 5a55317eb..5bafeba65 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -17,7 +17,7 @@
 namespace MOS::MOS6560 {
 
 // audio state
-class AudioGenerator: public ::Outputs::Speaker::SampleSource {
+class AudioGenerator: public ::Outputs::Speaker::SampleSource<AudioGenerator> {
 	public:
 		AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index 90c5c9b1f..48dcf6277 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -66,7 +66,7 @@ enum class Personality {
 
 	This AY has an attached mono or stereo mixer.
 */
-template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource {
+template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY38910<stereo>> {
 	public:
 		/// Creates a new AY38910.
 		AY38910(Personality, Concurrency::AsyncTaskQueue<false> &);
diff --git a/Components/AudioToggle/AudioToggle.hpp b/Components/AudioToggle/AudioToggle.hpp
index defd7a976..84cebb762 100644
--- a/Components/AudioToggle/AudioToggle.hpp
+++ b/Components/AudioToggle/AudioToggle.hpp
@@ -16,13 +16,14 @@ namespace Audio {
 /*!
 	Provides a sample source that can programmatically be set to one of two values.
 */
-class Toggle: public Outputs::Speaker::SampleSource {
+class Toggle: public Outputs::Speaker::SampleSource<Toggle> {
 	public:
 		Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
 		void skip_samples(const std::size_t number_of_samples);
+		static constexpr bool is_stereo = false;
 
 		void set_output(bool enabled);
 		bool get_output() const;
diff --git a/Components/KonamiSCC/KonamiSCC.hpp b/Components/KonamiSCC/KonamiSCC.hpp
index a0cb3ca30..a8c767f79 100644
--- a/Components/KonamiSCC/KonamiSCC.hpp
+++ b/Components/KonamiSCC/KonamiSCC.hpp
@@ -20,7 +20,7 @@ namespace Konami {
 	and five channels of output. The original SCC uses the same wave for channels
 	four and five, the SCC+ supports different waves for the two channels.
 */
-class SCC: public ::Outputs::Speaker::SampleSource {
+class SCC: public ::Outputs::Speaker::SampleSource<SCC> {
 	public:
 		/// Creates a new SCC.
 		SCC(Concurrency::AsyncTaskQueue<false> &task_queue);
diff --git a/Components/OPx/Implementation/OPLBase.hpp b/Components/OPx/Implementation/OPLBase.hpp
index a3067395c..98bee264f 100644
--- a/Components/OPx/Implementation/OPLBase.hpp
+++ b/Components/OPx/Implementation/OPLBase.hpp
@@ -13,7 +13,7 @@
 
 namespace Yamaha::OPL {
 
-template <typename Child> class OPLBase: public ::Outputs::Speaker::SampleSource {
+template <typename Child> class OPLBase: public ::Outputs::Speaker::SampleSource<Child> {
 	public:
 		void write(uint16_t address, uint8_t value) {
 			if(address & 1) {
diff --git a/Components/OPx/OPLL.hpp b/Components/OPx/OPLL.hpp
index 284c9ade9..5323fbeaf 100644
--- a/Components/OPx/OPLL.hpp
+++ b/Components/OPx/OPLL.hpp
@@ -27,6 +27,7 @@ class OPLL: public OPLBase<OPLL> {
 		/// As per ::SampleSource; provides audio output.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
+		static constexpr bool is_stereo = false;
 
 		// The OPLL is generally 'half' as loud as it's told to be. This won't strictly be true in
 		// rhythm mode, but it's correct for melodic output.
diff --git a/Components/SN76489/SN76489.hpp b/Components/SN76489/SN76489.hpp
index d720ee256..820170f3b 100644
--- a/Components/SN76489/SN76489.hpp
+++ b/Components/SN76489/SN76489.hpp
@@ -13,7 +13,7 @@
 
 namespace TI {
 
-class SN76489: public Outputs::Speaker::SampleSource {
+class SN76489: public Outputs::Speaker::SampleSource<SN76489> {
 	public:
 		enum class Personality {
 			SN76489,
diff --git a/Machines/Apple/AppleIIgs/Sound.hpp b/Machines/Apple/AppleIIgs/Sound.hpp
index 55c4f4c20..2eed23a8f 100644
--- a/Machines/Apple/AppleIIgs/Sound.hpp
+++ b/Machines/Apple/AppleIIgs/Sound.hpp
@@ -16,7 +16,7 @@
 
 namespace Apple::IIgs::Sound {
 
-class GLU: public Outputs::Speaker::SampleSource {
+class GLU: public Outputs::Speaker::SampleSource<GLU> {
 	public:
 		GLU(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -37,6 +37,7 @@ class GLU: public Outputs::Speaker::SampleSource {
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
 		void skip_samples(const std::size_t number_of_samples);
+		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index 3eabbc832..e23bcb16b 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -23,7 +23,7 @@ namespace Apple::Macintosh {
 	Designed to be clocked at half the rate of the real hardware — i.e.
 	a shade less than 4Mhz.
 */
-class Audio: public ::Outputs::Speaker::SampleSource {
+class Audio: public ::Outputs::Speaker::SampleSource<Audio> {
 	public:
 		Audio(Concurrency::AsyncTaskQueue<false> &task_queue);
 
diff --git a/Machines/Atari/2600/TIASound.hpp b/Machines/Atari/2600/TIASound.hpp
index 097b70f52..66a7cf95b 100644
--- a/Machines/Atari/2600/TIASound.hpp
+++ b/Machines/Atari/2600/TIASound.hpp
@@ -17,7 +17,7 @@ namespace Atari2600 {
 // will give greater resolution to changes in audio state. 1, 2 and 19 are the only divisors of 38.
 constexpr int CPUTicksPerAudioTick = 2;
 
-class TIASound: public Outputs::Speaker::SampleSource {
+class TIASound: public Outputs::Speaker::SampleSource<TIASound> {
 	public:
 		TIASound(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Machines/Electron/SoundGenerator.hpp b/Machines/Electron/SoundGenerator.hpp
index 2429bb37b..823291514 100644
--- a/Machines/Electron/SoundGenerator.hpp
+++ b/Machines/Electron/SoundGenerator.hpp
@@ -13,7 +13,7 @@
 
 namespace Electron {
 
-class SoundGenerator: public ::Outputs::Speaker::SampleSource {
+class SoundGenerator: public ::Outputs::Speaker::SampleSource<SoundGenerator> {
 	public:
 		SoundGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index 7b32f8db1..d5e8db1c5 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -26,7 +26,7 @@ enum class Interrupt: uint8_t {
 /*!
 	Models the audio-production subset of Dave's behaviour.
 */
-class Audio: public Outputs::Speaker::SampleSource {
+class Audio: public Outputs::Speaker::SampleSource<Audio> {
 	public:
 		Audio(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 52a0a3e71..1fa8c4ec0 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -21,9 +21,9 @@ namespace Outputs::Speaker {
 	An owner may optionally assign relative volumes.
 */
 template <typename... T> class CompoundSource:
-	public Outputs::Speaker::SampleSource {
+	public Outputs::Speaker::SampleSource<CompoundSource<T...>> {
 	private:
-		template <typename... S> class CompoundSourceHolder: public Outputs::Speaker::SampleSource {
+		template <typename... S> class CompoundSourceHolder: public Outputs::Speaker::SampleSource<CompoundSourceHolder<S...>> {
 			public:
 				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
 					std::memset(target, 0, sizeof(std::int16_t) * number_of_samples);
diff --git a/Outputs/Speaker/Implementation/SampleSource.hpp b/Outputs/Speaker/Implementation/SampleSource.hpp
index f9991e7ee..c356530df 100644
--- a/Outputs/Speaker/Implementation/SampleSource.hpp
+++ b/Outputs/Speaker/Implementation/SampleSource.hpp
@@ -8,16 +8,22 @@
 
 #pragma once
 
+#include <array>
 #include <cstddef>
 #include <cstdint>
 
 namespace Outputs::Speaker {
 
+template <bool stereo> struct SampleT;
+template <> struct SampleT<true> { using type = std::array<std::uint16_t, 2>; };
+template <> struct SampleT<false> { using type = std::uint16_t; };
+
 /*!
 	A sample source is something that can provide a stream of audio.
 	This optional base class provides the interface expected to be exposed
 	by the template parameter to LowpassSpeaker.
 */
+template <typename SourceT>
 class SampleSource {
 	public:
 		/*!
@@ -54,7 +60,7 @@ class SampleSource {
 		/*!
 			Indicates whether this component will write stereo samples.
 		*/
-		static constexpr bool is_stereo = false;
+		static constexpr bool is_stereo = SourceT::is_stereo;
 
 		/*!
 			Permits a sample source to declare that, averaged over time, it will use only

From f4d8c04f3ca4d077d8c4c8cb86b50d9d708bad71 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 1 Feb 2024 21:56:33 -0500
Subject: [PATCH 04/20] Without yet much exposition, draft sample-by-sample
 interface.

---
 .../Speaker/Implementation/SampleSource.hpp   | 44 ++++++++++++++-----
 1 file changed, 34 insertions(+), 10 deletions(-)

diff --git a/Outputs/Speaker/Implementation/SampleSource.hpp b/Outputs/Speaker/Implementation/SampleSource.hpp
index c356530df..29dc70834 100644
--- a/Outputs/Speaker/Implementation/SampleSource.hpp
+++ b/Outputs/Speaker/Implementation/SampleSource.hpp
@@ -15,8 +15,8 @@
 namespace Outputs::Speaker {
 
 template <bool stereo> struct SampleT;
-template <> struct SampleT<true> { using type = std::array<std::uint16_t, 2>; };
-template <> struct SampleT<false> { using type = std::uint16_t; };
+template <> struct SampleT<true> { using type = std::array<std::int16_t, 2>; };
+template <> struct SampleT<false> { using type = std::int16_t; };
 
 /*!
 	A sample source is something that can provide a stream of audio.
@@ -26,10 +26,28 @@ template <> struct SampleT<false> { using type = std::uint16_t; };
 template <typename SourceT>
 class SampleSource {
 	public:
+		/*!
+			Indicates whether this component will write stereo samples.
+		*/
+		static constexpr bool is_stereo = SourceT::is_stereo;
+
 		/*!
 			Should write the next @c number_of_samples to @c target.
 		*/
-		void get_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] std::int16_t *target) {}
+		void get_samples(std::size_t number_of_samples, std::int16_t *target) {
+			const auto &source = *static_cast<SourceT *>(this);
+			while(number_of_samples--) {
+				if constexpr (is_stereo) {
+					const auto next = source.level();
+					target[0] = next[0];
+					target[1] = next[1];
+					target += 2;
+				} else {
+					*target = source.level();
+					++target;
+				}
+			}
+		}
 
 		/*!
 			Should skip the next @c number_of_samples. Subclasses of this SampleSource
@@ -38,6 +56,9 @@ class SampleSource {
 			implementation below.
 		*/
 		void skip_samples(const std::size_t number_of_samples) {
+			if constexpr (&SourceT::advance == &SampleSource<SourceT>::advance) {
+				return;
+			}
 			std::int16_t scratch_pad[number_of_samples];
 			get_samples(number_of_samples, scratch_pad);
 		}
@@ -47,9 +68,17 @@ class SampleSource {
 				fill the target with zeroes; @c false if a call might return all zeroes or
 				might not.
 		*/
-		bool is_zero_level() const {
-			return false;
+		bool is_zero_level() const						{	return false;	}
+		auto level() const	{
+			typename SampleT<is_stereo>::type result;
+			if constexpr (is_stereo) {
+				result[0] = result[1] = 0;
+			} else {
+				result = 0;
+			}
+			return result;
 		}
+		void advance()									{}
 
 		/*!
 			Sets the proper output range for this sample source; it should write values
@@ -57,11 +86,6 @@ class SampleSource {
 		*/
 		void set_sample_volume_range([[maybe_unused]] std::int16_t volume) {}
 
-		/*!
-			Indicates whether this component will write stereo samples.
-		*/
-		static constexpr bool is_stereo = SourceT::is_stereo;
-
 		/*!
 			Permits a sample source to declare that, averaged over time, it will use only
 			a certain proportion of the allocated volume range. This commonly happens

From 228012cd0cccdf8560ba1f790c6fb78fbdb3efba Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 1 Feb 2024 22:03:13 -0500
Subject: [PATCH 05/20] Make a further deployment of `std::fill`.

---
 Machines/Apple/Macintosh/Audio.cpp | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/Machines/Apple/Macintosh/Audio.cpp b/Machines/Apple/Macintosh/Audio.cpp
index d24497990..caa312248 100644
--- a/Machines/Apple/Macintosh/Audio.cpp
+++ b/Machines/Apple/Macintosh/Audio.cpp
@@ -8,6 +8,8 @@
 
 #include "Audio.hpp"
 
+#include <algorithm>
+
 using namespace Apple::Macintosh;
 
 namespace {
@@ -79,11 +81,8 @@ void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
 		const auto cycles_left_in_sample = std::min(number_of_samples, sample_length - subcycle_offset_);
 
 		// Determine the output level, and output that many samples.
-		// (Hoping that the copiler substitutes an effective memset16-type operation here).
 		const int16_t output_level = volume_multiplier_ * (int16_t(sample_queue_.buffer[sample_queue_.read_pointer].load(std::memory_order::memory_order_relaxed)) - 128);
-		for(size_t c = 0; c < cycles_left_in_sample; ++c) {
-			target[c] = output_level;
-		}
+		std::fill(target, target + cycles_left_in_sample, output_level);
 		target += cycles_left_in_sample;
 
 		// Advance the sample pointer.

From d481f335b8f24fc27180b83a5bdd65e334905919 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 8 Feb 2024 10:47:05 -0500
Subject: [PATCH 06/20] Switch to another std::fill.

---
 Outputs/Speaker/Implementation/CompoundSource.hpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 1fa8c4ec0..585ab0c1f 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -10,6 +10,7 @@
 
 #include "SampleSource.hpp"
 
+#include <algorithm>
 #include <cassert>
 #include <cstring>
 #include <atomic>
@@ -26,7 +27,7 @@ template <typename... T> class CompoundSource:
 		template <typename... S> class CompoundSourceHolder: public Outputs::Speaker::SampleSource<CompoundSourceHolder<S...>> {
 			public:
 				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
-					std::memset(target, 0, sizeof(std::int16_t) * number_of_samples);
+					std::fill(target, target + number_of_samples, 0);
 				}
 
 				void set_scaled_volume_range(int16_t, double *, double) {}

From 147d817977cf7811f822b69ad093083e0f0b3a85 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 8 Feb 2024 11:10:08 -0500
Subject: [PATCH 07/20] Use fold expression for final-answer is_stereo.

---
 Outputs/Speaker/Implementation/CompoundSource.hpp | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 585ab0c1f..d46fc14ed 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -17,6 +17,15 @@
 
 namespace Outputs::Speaker {
 
+/// @returns @c true if any of the templated sources is stereo; @c false otherwise.
+template <typename... S> constexpr bool is_stereo() {
+	bool is_stereo = false;
+	([&] {
+		is_stereo |= S::is_stereo;
+	}(), ...);
+	return is_stereo;
+}
+
 /*!
 	A CompoundSource adds together the sound generated by multiple individual SampleSources.
 	An owner may optionally assign relative volumes.
@@ -148,7 +157,7 @@ template <typename... T> class CompoundSource:
 		/*!
 			@c true if any of the sources owned by this CompoundSource is stereo.
 		*/
-		static constexpr bool is_stereo = CompoundSourceHolder<T...>::is_stereo;
+		static constexpr bool is_stereo = ::Outputs::Speaker::is_stereo<T...>();
 
 		/*!
 			@returns the average output peak given the sources owned by this CompoundSource and the

From 48be7c677e6aa2a52c18ca2d1a7b0ed9c8d8057c Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 8 Feb 2024 12:07:12 -0500
Subject: [PATCH 08/20] Avoid inheritance.

---
 Outputs/Speaker/Implementation/CompoundSource.hpp | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index d46fc14ed..b6e7b21d9 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -33,13 +33,14 @@ template <typename... S> constexpr bool is_stereo() {
 template <typename... T> class CompoundSource:
 	public Outputs::Speaker::SampleSource<CompoundSource<T...>> {
 	private:
-		template <typename... S> class CompoundSourceHolder: public Outputs::Speaker::SampleSource<CompoundSourceHolder<S...>> {
+		template <typename... S> class CompoundSourceHolder {
 			public:
 				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
 					std::fill(target, target + number_of_samples, 0);
 				}
 
 				void set_scaled_volume_range(int16_t, double *, double) {}
+				void skip_samples(const std::size_t) {}
 
 				static constexpr std::size_t size() {
 					return 0;

From a4a983eb81448d0d773548909bd6a9c3e1346e28 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Thu, 8 Feb 2024 15:21:47 -0500
Subject: [PATCH 09/20] Promote stereo status to template parameter.

---
 Components/6560/6560.hpp                          |  3 +--
 Components/AY38910/AY38910.hpp                    |  3 +--
 Components/AudioToggle/AudioToggle.hpp            |  3 +--
 Components/KonamiSCC/KonamiSCC.hpp                |  3 +--
 Components/OPx/Implementation/OPLBase.hpp         |  2 +-
 Components/OPx/OPLL.hpp                           |  5 ++---
 Components/SN76489/SN76489.hpp                    |  3 +--
 Machines/Apple/AppleIIgs/Sound.hpp                |  3 +--
 Machines/Apple/Macintosh/Audio.hpp                |  3 +--
 Machines/Atari/2600/TIASound.hpp                  |  3 +--
 Machines/Electron/SoundGenerator.hpp              |  3 +--
 Machines/Enterprise/Dave.hpp                      |  3 +--
 Outputs/Speaker/Implementation/CompoundSource.hpp | 13 ++++---------
 Outputs/Speaker/Implementation/SampleSource.hpp   |  6 +++---
 14 files changed, 20 insertions(+), 36 deletions(-)

diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index 5bafeba65..0995c2545 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -17,7 +17,7 @@
 namespace MOS::MOS6560 {
 
 // audio state
-class AudioGenerator: public ::Outputs::Speaker::SampleSource<AudioGenerator> {
+class AudioGenerator: public ::Outputs::Speaker::SampleSource<AudioGenerator, false> {
 	public:
 		AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -28,7 +28,6 @@ class AudioGenerator: public ::Outputs::Speaker::SampleSource<AudioGenerator> {
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		void skip_samples(std::size_t number_of_samples);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index 48dcf6277..f9ffe1476 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -66,7 +66,7 @@ enum class Personality {
 
 	This AY has an attached mono or stereo mixer.
 */
-template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY38910<stereo>> {
+template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY38910<stereo>, stereo> {
 	public:
 		/// Creates a new AY38910.
 		AY38910(Personality, Concurrency::AsyncTaskQueue<false> &);
@@ -109,7 +109,6 @@ template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = stereo;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &task_queue_;
diff --git a/Components/AudioToggle/AudioToggle.hpp b/Components/AudioToggle/AudioToggle.hpp
index 84cebb762..26ef7007e 100644
--- a/Components/AudioToggle/AudioToggle.hpp
+++ b/Components/AudioToggle/AudioToggle.hpp
@@ -16,14 +16,13 @@ namespace Audio {
 /*!
 	Provides a sample source that can programmatically be set to one of two values.
 */
-class Toggle: public Outputs::Speaker::SampleSource<Toggle> {
+class Toggle: public Outputs::Speaker::SampleSource<Toggle, false> {
 	public:
 		Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
 		void skip_samples(const std::size_t number_of_samples);
-		static constexpr bool is_stereo = false;
 
 		void set_output(bool enabled);
 		bool get_output() const;
diff --git a/Components/KonamiSCC/KonamiSCC.hpp b/Components/KonamiSCC/KonamiSCC.hpp
index a8c767f79..8d2986e85 100644
--- a/Components/KonamiSCC/KonamiSCC.hpp
+++ b/Components/KonamiSCC/KonamiSCC.hpp
@@ -20,7 +20,7 @@ namespace Konami {
 	and five channels of output. The original SCC uses the same wave for channels
 	four and five, the SCC+ supports different waves for the two channels.
 */
-class SCC: public ::Outputs::Speaker::SampleSource<SCC> {
+class SCC: public ::Outputs::Speaker::SampleSource<SCC, false> {
 	public:
 		/// Creates a new SCC.
 		SCC(Concurrency::AsyncTaskQueue<false> &task_queue);
@@ -31,7 +31,6 @@ class SCC: public ::Outputs::Speaker::SampleSource<SCC> {
 		/// As per ::SampleSource; provides audio output.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = false;
 
 		/// Writes to the SCC.
 		void write(uint16_t address, uint8_t value);
diff --git a/Components/OPx/Implementation/OPLBase.hpp b/Components/OPx/Implementation/OPLBase.hpp
index 98bee264f..569e970a2 100644
--- a/Components/OPx/Implementation/OPLBase.hpp
+++ b/Components/OPx/Implementation/OPLBase.hpp
@@ -13,7 +13,7 @@
 
 namespace Yamaha::OPL {
 
-template <typename Child> class OPLBase: public ::Outputs::Speaker::SampleSource<Child> {
+template <typename Child, bool stereo> class OPLBase: public ::Outputs::Speaker::SampleSource<Child, stereo> {
 	public:
 		void write(uint16_t address, uint8_t value) {
 			if(address & 1) {
diff --git a/Components/OPx/OPLL.hpp b/Components/OPx/OPLL.hpp
index 5323fbeaf..8d35e8e1b 100644
--- a/Components/OPx/OPLL.hpp
+++ b/Components/OPx/OPLL.hpp
@@ -19,7 +19,7 @@
 
 namespace Yamaha::OPL {
 
-class OPLL: public OPLBase<OPLL> {
+class OPLL: public OPLBase<OPLL, false> {
 	public:
 		/// Creates a new OPLL or VRC7.
 		OPLL(Concurrency::AsyncTaskQueue<false> &task_queue, int audio_divider = 1, bool is_vrc7 = false);
@@ -27,7 +27,6 @@ class OPLL: public OPLBase<OPLL> {
 		/// As per ::SampleSource; provides audio output.
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = false;
 
 		// The OPLL is generally 'half' as loud as it's told to be. This won't strictly be true in
 		// rhythm mode, but it's correct for melodic output.
@@ -37,7 +36,7 @@ class OPLL: public OPLBase<OPLL> {
 		uint8_t read(uint16_t address);
 
 	private:
-		friend OPLBase<OPLL>;
+		friend OPLBase<OPLL, false>;
 		void write_register(uint8_t address, uint8_t value);
 
 		int audio_divider_ = 0;
diff --git a/Components/SN76489/SN76489.hpp b/Components/SN76489/SN76489.hpp
index 820170f3b..cab4469e1 100644
--- a/Components/SN76489/SN76489.hpp
+++ b/Components/SN76489/SN76489.hpp
@@ -13,7 +13,7 @@
 
 namespace TI {
 
-class SN76489: public Outputs::Speaker::SampleSource<SN76489> {
+class SN76489: public Outputs::Speaker::SampleSource<SN76489, false> {
 	public:
 		enum class Personality {
 			SN76489,
@@ -31,7 +31,6 @@ class SN76489: public Outputs::Speaker::SampleSource<SN76489> {
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = false;
 
 	private:
 		int master_divider_ = 0;
diff --git a/Machines/Apple/AppleIIgs/Sound.hpp b/Machines/Apple/AppleIIgs/Sound.hpp
index 2eed23a8f..dece2832d 100644
--- a/Machines/Apple/AppleIIgs/Sound.hpp
+++ b/Machines/Apple/AppleIIgs/Sound.hpp
@@ -16,7 +16,7 @@
 
 namespace Apple::IIgs::Sound {
 
-class GLU: public Outputs::Speaker::SampleSource<GLU> {
+class GLU: public Outputs::Speaker::SampleSource<GLU, false> {	// TODO: isn't this stereo?
 	public:
 		GLU(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -37,7 +37,6 @@ class GLU: public Outputs::Speaker::SampleSource<GLU> {
 		void get_samples(std::size_t number_of_samples, std::int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
 		void skip_samples(const std::size_t number_of_samples);
-		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index e23bcb16b..d7cbcaae0 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -23,7 +23,7 @@ namespace Apple::Macintosh {
 	Designed to be clocked at half the rate of the real hardware — i.e.
 	a shade less than 4Mhz.
 */
-class Audio: public ::Outputs::Speaker::SampleSource<Audio> {
+class Audio: public ::Outputs::Speaker::SampleSource<Audio, false> {
 	public:
 		Audio(Concurrency::AsyncTaskQueue<false> &task_queue);
 
@@ -53,7 +53,6 @@ class Audio: public ::Outputs::Speaker::SampleSource<Audio> {
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
-		constexpr static bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &task_queue_;
diff --git a/Machines/Atari/2600/TIASound.hpp b/Machines/Atari/2600/TIASound.hpp
index 66a7cf95b..fdbbc3bfd 100644
--- a/Machines/Atari/2600/TIASound.hpp
+++ b/Machines/Atari/2600/TIASound.hpp
@@ -17,7 +17,7 @@ namespace Atari2600 {
 // will give greater resolution to changes in audio state. 1, 2 and 19 are the only divisors of 38.
 constexpr int CPUTicksPerAudioTick = 2;
 
-class TIASound: public Outputs::Speaker::SampleSource<TIASound> {
+class TIASound: public Outputs::Speaker::SampleSource<TIASound, false> {
 	public:
 		TIASound(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -28,7 +28,6 @@ class TIASound: public Outputs::Speaker::SampleSource<TIASound> {
 		// To satisfy ::SampleSource.
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Machines/Electron/SoundGenerator.hpp b/Machines/Electron/SoundGenerator.hpp
index 823291514..666c4c0c8 100644
--- a/Machines/Electron/SoundGenerator.hpp
+++ b/Machines/Electron/SoundGenerator.hpp
@@ -13,7 +13,7 @@
 
 namespace Electron {
 
-class SoundGenerator: public ::Outputs::Speaker::SampleSource<SoundGenerator> {
+class SoundGenerator: public ::Outputs::Speaker::SampleSource<SoundGenerator, false> {
 	public:
 		SoundGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -27,7 +27,6 @@ class SoundGenerator: public ::Outputs::Speaker::SampleSource<SoundGenerator> {
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 		void skip_samples(std::size_t number_of_samples);
 		void set_sample_volume_range(std::int16_t range);
-		static constexpr bool is_stereo = false;
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index d5e8db1c5..aad6423b6 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -26,7 +26,7 @@ enum class Interrupt: uint8_t {
 /*!
 	Models the audio-production subset of Dave's behaviour.
 */
-class Audio: public Outputs::Speaker::SampleSource<Audio> {
+class Audio: public Outputs::Speaker::SampleSource<Audio, true> {
 	public:
 		Audio(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -37,7 +37,6 @@ class Audio: public Outputs::Speaker::SampleSource<Audio> {
 
 		// MARK: - SampleSource.
 		void set_sample_volume_range(int16_t range);
-		static constexpr bool is_stereo = true;
 		void get_samples(std::size_t number_of_samples, int16_t *target);
 
 	private:
diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index b6e7b21d9..1c053b90b 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -31,7 +31,7 @@ template <typename... S> constexpr bool is_stereo() {
 	An owner may optionally assign relative volumes.
 */
 template <typename... T> class CompoundSource:
-	public Outputs::Speaker::SampleSource<CompoundSource<T...>> {
+	public Outputs::Speaker::SampleSource<CompoundSource<T...>, ::Outputs::Speaker::is_stereo<T...>()> {
 	private:
 		template <typename... S> class CompoundSourceHolder {
 			public:
@@ -57,6 +57,8 @@ template <typename... T> class CompoundSource:
 			public:
 				CompoundSourceHolder(S &source, R &...next) : source_(source), next_source_(next...) {}
 
+				static constexpr bool is_stereo = S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
+
 				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
 					// Get the rest of the output.
 					next_source_.template get_samples<output_stereo>(number_of_samples, target);
@@ -107,8 +109,6 @@ template <typename... T> class CompoundSource:
 					return 1 + CompoundSourceHolder<R...>::size();
 				}
 
-				static constexpr bool is_stereo =  S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
-
 				double total_scale(double *volumes) const {
 					return (volumes[0] / source_.average_output_peak()) + next_source_.total_scale(&volumes[1]);
 				}
@@ -128,7 +128,7 @@ template <typename... T> class CompoundSource:
 		}
 
 		void get_samples(std::size_t number_of_samples, std::int16_t *target) {
-			source_holder_.template get_samples<is_stereo>(number_of_samples, target);
+			source_holder_.template get_samples<::Outputs::Speaker::is_stereo<T...>()>(number_of_samples, target);
 		}
 
 		void skip_samples(const std::size_t number_of_samples) {
@@ -155,11 +155,6 @@ template <typename... T> class CompoundSource:
 			average_output_peak_ = 1.0 / source_holder_.total_scale(volumes_.data());
 		}
 
-		/*!
-			@c true if any of the sources owned by this CompoundSource is stereo.
-		*/
-		static constexpr bool is_stereo = ::Outputs::Speaker::is_stereo<T...>();
-
 		/*!
 			@returns the average output peak given the sources owned by this CompoundSource and the
 				current relative volumes.
diff --git a/Outputs/Speaker/Implementation/SampleSource.hpp b/Outputs/Speaker/Implementation/SampleSource.hpp
index 29dc70834..5353db641 100644
--- a/Outputs/Speaker/Implementation/SampleSource.hpp
+++ b/Outputs/Speaker/Implementation/SampleSource.hpp
@@ -23,13 +23,13 @@ template <> struct SampleT<false> { using type = std::int16_t; };
 	This optional base class provides the interface expected to be exposed
 	by the template parameter to LowpassSpeaker.
 */
-template <typename SourceT>
+template <typename SourceT, bool stereo>
 class SampleSource {
 	public:
 		/*!
 			Indicates whether this component will write stereo samples.
 		*/
-		static constexpr bool is_stereo = SourceT::is_stereo;
+		static constexpr bool is_stereo = stereo;
 
 		/*!
 			Should write the next @c number_of_samples to @c target.
@@ -56,7 +56,7 @@ class SampleSource {
 			implementation below.
 		*/
 		void skip_samples(const std::size_t number_of_samples) {
-			if constexpr (&SourceT::advance == &SampleSource<SourceT>::advance) {
+			if constexpr (&SourceT::advance == &SampleSource<SourceT, stereo>::advance) {
 				return;
 			}
 			std::int16_t scratch_pad[number_of_samples];

From f3d0827d140af64db01e7248636ba6f3eb1344c4 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 9 Feb 2024 09:15:48 -0500
Subject: [PATCH 10/20] Introduce [Mono/Stereo]Sample types.

---
 Components/6560/6560.hpp                      |  4 +--
 Components/AY38910/AY38910.cpp                | 26 +++++++--------
 Components/AY38910/AY38910.hpp                |  4 +--
 Components/AudioToggle/AudioToggle.hpp        |  2 +-
 Machines/Enterprise/Dave.cpp                  | 18 ++++------
 Machines/Enterprise/Dave.hpp                  |  2 +-
 .../Speaker/Implementation/LowpassSpeaker.hpp |  7 +++-
 .../Speaker/Implementation/SampleSource.hpp   | 33 +++++--------------
 Outputs/Speaker/Speaker.hpp                   |  8 +++++
 9 files changed, 45 insertions(+), 59 deletions(-)

diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index 0995c2545..24d8e5479 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -17,7 +17,7 @@
 namespace MOS::MOS6560 {
 
 // audio state
-class AudioGenerator: public ::Outputs::Speaker::SampleSource<AudioGenerator, false> {
+class AudioGenerator: public Outputs::Speaker::SampleSource<AudioGenerator, false> {
 	public:
 		AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
@@ -25,7 +25,7 @@ class AudioGenerator: public ::Outputs::Speaker::SampleSource<AudioGenerator, fa
 		void set_control(int channel, uint8_t value);
 
 		// For ::SampleSource.
-		void get_samples(std::size_t number_of_samples, int16_t *target);
+		void get_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void skip_samples(std::size_t number_of_samples);
 		void set_sample_volume_range(std::int16_t range);
 
diff --git a/Components/AY38910/AY38910.cpp b/Components/AY38910/AY38910.cpp
index f02048469..83168b287 100644
--- a/Components/AY38910/AY38910.cpp
+++ b/Components/AY38910/AY38910.cpp
@@ -101,7 +101,11 @@ template <bool is_stereo> void AY38910<is_stereo>::set_output_mixing(float a_lef
 	c_right_ = uint8_t(c_right * 255.0f);
 }
 
-template <bool is_stereo> void AY38910<is_stereo>::get_samples(std::size_t number_of_samples, int16_t *target) {
+template <bool is_stereo>
+void AY38910<is_stereo>::get_samples(
+	std::size_t number_of_samples,
+	typename Outputs::Speaker::SampleT<is_stereo>::type *target
+) {
 	// Note on structure below: the real AY has a built-in divider of 8
 	// prior to applying its tone and noise dividers. But the YM fills the
 	// same total periods for noise and tone with double-precision envelopes.
@@ -113,11 +117,7 @@ template <bool is_stereo> void AY38910<is_stereo>::get_samples(std::size_t numbe
 
 	std::size_t c = 0;
 	while((master_divider_&3) && c < number_of_samples) {
-		if constexpr (is_stereo) {
-			reinterpret_cast<uint32_t *>(target)[c] = output_volume_;
-		} else {
-			target[c] = int16_t(output_volume_);
-		}
+		target[c] = output_volume_;
 		master_divider_++;
 		c++;
 	}
@@ -159,11 +159,7 @@ template <bool is_stereo> void AY38910<is_stereo>::get_samples(std::size_t numbe
 		evaluate_output_volume();
 
 		for(int ic = 0; ic < 4 && c < number_of_samples; ic++) {
-			if constexpr (is_stereo) {
-				reinterpret_cast<uint32_t *>(target)[c] = output_volume_;
-			} else {
-				target[c] = int16_t(output_volume_);
-			}
+			target[c] = output_volume_;
 			c++;
 			master_divider_++;
 		}
@@ -214,19 +210,19 @@ template <bool is_stereo> void AY38910<is_stereo>::evaluate_output_volume() {
 
 	// Mix additively, weighting if in stereo.
 	if constexpr (is_stereo) {
-		int16_t *const output_volumes = reinterpret_cast<int16_t *>(&output_volume_);
-		output_volumes[0] = int16_t((
+//		int16_t *const output_volumes = reinterpret_cast<int16_t *>(&output_volume_);
+		output_volume_[0] = int16_t((
 			volumes_[volumes[0]] * channel_levels[0] * a_left_ +
 			volumes_[volumes[1]] * channel_levels[1] * b_left_ +
 			volumes_[volumes[2]] * channel_levels[2] * c_left_
 		) >> 8);
-		output_volumes[1] = int16_t((
+		output_volume_[1] = int16_t((
 			volumes_[volumes[0]] * channel_levels[0] * a_right_ +
 			volumes_[volumes[1]] * channel_levels[1] * b_right_ +
 			volumes_[volumes[2]] * channel_levels[2] * c_right_
 		) >> 8);
 	} else {
-		output_volume_ = uint32_t(
+		output_volume_ = int16_t(
 			volumes_[volumes[0]] * channel_levels[0] +
 			volumes_[volumes[1]] * channel_levels[1] +
 			volumes_[volumes[2]] * channel_levels[2]
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index f9ffe1476..58eb4ec80 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -106,7 +106,7 @@ template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY
 		void set_output_mixing(float a_left, float b_left, float c_left, float a_right = 1.0, float b_right = 1.0, float c_right = 1.0);
 
 		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter.
-		void get_samples(std::size_t number_of_samples, int16_t *target);
+		void get_samples(std::size_t number_of_samples, typename Outputs::Speaker::SampleT<stereo>::type *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
 
@@ -149,7 +149,7 @@ template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY
 
 		uint8_t data_input_, data_output_;
 
-		uint32_t output_volume_;
+		typename Outputs::Speaker::SampleT<stereo>::type output_volume_;
 
 		void update_bus();
 		PortHandler *port_handler_ = nullptr;
diff --git a/Components/AudioToggle/AudioToggle.hpp b/Components/AudioToggle/AudioToggle.hpp
index 26ef7007e..b93ea4cae 100644
--- a/Components/AudioToggle/AudioToggle.hpp
+++ b/Components/AudioToggle/AudioToggle.hpp
@@ -20,7 +20,7 @@ class Toggle: public Outputs::Speaker::SampleSource<Toggle, false> {
 	public:
 		Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
-		void get_samples(std::size_t number_of_samples, std::int16_t *target);
+		void get_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
 		void skip_samples(const std::size_t number_of_samples);
 
diff --git a/Machines/Enterprise/Dave.cpp b/Machines/Enterprise/Dave.cpp
index e619f6352..940755014 100644
--- a/Machines/Enterprise/Dave.cpp
+++ b/Machines/Enterprise/Dave.cpp
@@ -99,17 +99,14 @@ void Audio::update_channel(int c) {
 	channels_[c].output |= output;
 }
 
-void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
-	struct Frame {
-		int16_t left, right;
-	} output_level;
-	Frame *target_frames = reinterpret_cast<Frame *>(target);
+void Audio::get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target) {
+	Outputs::Speaker::StereoSample output_level;
 
 	size_t c = 0;
 	while(c < number_of_samples) {
 		// I'm unclear on the details of the time division multiplexing so,
 		// for now, just sum the outputs.
-		output_level.left =
+		output_level[0] =
 			volume_ *
 				(use_direct_output_[0] ?
 					channels_[0].amplitude[0]
@@ -120,7 +117,7 @@ void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
 						noise_.amplitude[0] * noise_.final_output
 				));
 
-		output_level.right =
+		output_level[1] =
 			volume_ *
 				(use_direct_output_[1] ?
 					channels_[0].amplitude[1]
@@ -133,14 +130,11 @@ void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
 
 		while(global_divider_ && c < number_of_samples) {
 			--global_divider_;
-			target_frames[c] = output_level;
+			target[c] = output_level;
 			++c;
 		}
-
 		global_divider_ = global_divider_reload_;
-		if(!global_divider_) {
-			global_divider_ = global_divider_reload_;
-		}
+
 		poly_state_[int(Channel::Distortion::FourBit)] = poly4_.next();
 		poly_state_[int(Channel::Distortion::FiveBit)] = poly5_.next();
 		poly_state_[int(Channel::Distortion::SevenBit)] = poly7_.next();
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index aad6423b6..a3e369251 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -37,7 +37,7 @@ class Audio: public Outputs::Speaker::SampleSource<Audio, true> {
 
 		// MARK: - SampleSource.
 		void set_sample_volume_range(int16_t range);
-		void get_samples(std::size_t number_of_samples, int16_t *target);
+		void get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target);
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/Outputs/Speaker/Implementation/LowpassSpeaker.hpp b/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
index 3b64dfcc6..5634de15d 100644
--- a/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
+++ b/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
@@ -404,7 +404,12 @@ template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpa
 		}
 
 		void get_samples(size_t length, int16_t *target) {
-			sample_source_.get_samples(length, target);
+			if constexpr (SampleSource::is_stereo) {
+				StereoSample *const stereo_target = reinterpret_cast<StereoSample *>(target);
+				sample_source_.get_samples(length, stereo_target);
+			} else {
+				sample_source_.get_samples(length, target);
+			}
 		}
 };
 
diff --git a/Outputs/Speaker/Implementation/SampleSource.hpp b/Outputs/Speaker/Implementation/SampleSource.hpp
index 5353db641..36afe40f7 100644
--- a/Outputs/Speaker/Implementation/SampleSource.hpp
+++ b/Outputs/Speaker/Implementation/SampleSource.hpp
@@ -12,11 +12,9 @@
 #include <cstddef>
 #include <cstdint>
 
-namespace Outputs::Speaker {
+#include "../Speaker.hpp"
 
-template <bool stereo> struct SampleT;
-template <> struct SampleT<true> { using type = std::array<std::int16_t, 2>; };
-template <> struct SampleT<false> { using type = std::int16_t; };
+namespace Outputs::Speaker {
 
 /*!
 	A sample source is something that can provide a stream of audio.
@@ -34,18 +32,11 @@ class SampleSource {
 		/*!
 			Should write the next @c number_of_samples to @c target.
 		*/
-		void get_samples(std::size_t number_of_samples, std::int16_t *target) {
+		void get_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target) {
 			const auto &source = *static_cast<SourceT *>(this);
 			while(number_of_samples--) {
-				if constexpr (is_stereo) {
-					const auto next = source.level();
-					target[0] = next[0];
-					target[1] = next[1];
-					target += 2;
-				} else {
-					*target = source.level();
-					++target;
-				}
+				*target = source.level();
+				++target;
 			}
 		}
 
@@ -59,7 +50,7 @@ class SampleSource {
 			if constexpr (&SourceT::advance == &SampleSource<SourceT, stereo>::advance) {
 				return;
 			}
-			std::int16_t scratch_pad[number_of_samples];
+			typename SampleT<stereo>::type scratch_pad[number_of_samples];
 			get_samples(number_of_samples, scratch_pad);
 		}
 
@@ -68,16 +59,8 @@ class SampleSource {
 				fill the target with zeroes; @c false if a call might return all zeroes or
 				might not.
 		*/
-		bool is_zero_level() const						{	return false;	}
-		auto level() const	{
-			typename SampleT<is_stereo>::type result;
-			if constexpr (is_stereo) {
-				result[0] = result[1] = 0;
-			} else {
-				result = 0;
-			}
-			return result;
-		}
+		bool is_zero_level() const						{	return false;					}
+		auto level() const								{	return typename SampleT<stereo>::type();	}
 		void advance()									{}
 
 		/*!
diff --git a/Outputs/Speaker/Speaker.hpp b/Outputs/Speaker/Speaker.hpp
index c35b182c1..d65a54fc4 100644
--- a/Outputs/Speaker/Speaker.hpp
+++ b/Outputs/Speaker/Speaker.hpp
@@ -14,6 +14,14 @@
 
 namespace Outputs::Speaker {
 
+template <bool stereo> struct SampleT;
+template <> struct SampleT<true> { using type = std::array<std::int16_t, 2>; };	// TODO: adopt left/right as per Dave?
+template <> struct SampleT<false> { using type = std::int16_t; };
+
+// Shorthands.
+using MonoSample = SampleT<false>::type;
+using StereoSample = SampleT<true>::type;
+
 /*!
 	Provides a communication point for sound; machines that have a speaker provide an
 	audio output.

From c105acf1c78102f98f738d622b871dc2061e4e79 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 9 Feb 2024 10:48:42 -0500
Subject: [PATCH 11/20] Adopt a full type for stereo samples, gaining + and +=.

---
 Components/AY38910/AY38910.cpp                |  5 +--
 Machines/Enterprise/Dave.cpp                  |  4 +-
 .../xcschemes/Clock Signal.xcscheme           |  2 +-
 .../Speaker/Implementation/CompoundSource.hpp |  8 ++--
 Outputs/Speaker/Speaker.hpp                   | 37 ++++++++++++++++---
 5 files changed, 41 insertions(+), 15 deletions(-)

diff --git a/Components/AY38910/AY38910.cpp b/Components/AY38910/AY38910.cpp
index 83168b287..e2ad41467 100644
--- a/Components/AY38910/AY38910.cpp
+++ b/Components/AY38910/AY38910.cpp
@@ -210,13 +210,12 @@ template <bool is_stereo> void AY38910<is_stereo>::evaluate_output_volume() {
 
 	// Mix additively, weighting if in stereo.
 	if constexpr (is_stereo) {
-//		int16_t *const output_volumes = reinterpret_cast<int16_t *>(&output_volume_);
-		output_volume_[0] = int16_t((
+		output_volume_.left = int16_t((
 			volumes_[volumes[0]] * channel_levels[0] * a_left_ +
 			volumes_[volumes[1]] * channel_levels[1] * b_left_ +
 			volumes_[volumes[2]] * channel_levels[2] * c_left_
 		) >> 8);
-		output_volume_[1] = int16_t((
+		output_volume_.right = int16_t((
 			volumes_[volumes[0]] * channel_levels[0] * a_right_ +
 			volumes_[volumes[1]] * channel_levels[1] * b_right_ +
 			volumes_[volumes[2]] * channel_levels[2] * c_right_
diff --git a/Machines/Enterprise/Dave.cpp b/Machines/Enterprise/Dave.cpp
index 940755014..ba079087b 100644
--- a/Machines/Enterprise/Dave.cpp
+++ b/Machines/Enterprise/Dave.cpp
@@ -106,7 +106,7 @@ void Audio::get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoS
 	while(c < number_of_samples) {
 		// I'm unclear on the details of the time division multiplexing so,
 		// for now, just sum the outputs.
-		output_level[0] =
+		output_level.left =
 			volume_ *
 				(use_direct_output_[0] ?
 					channels_[0].amplitude[0]
@@ -117,7 +117,7 @@ void Audio::get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoS
 						noise_.amplitude[0] * noise_.final_output
 				));
 
-		output_level[1] =
+		output_level.right =
 			volume_ *
 				(use_direct_output_[1] ?
 					channels_[0].amplitude[1]
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme
index 474fa352e..19b54b90e 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
@@ -62,7 +62,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Debug"
+      buildConfiguration = "Release"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"
diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 1c053b90b..16d33657f 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -59,7 +59,9 @@ template <typename... T> class CompoundSource:
 
 				static constexpr bool is_stereo = S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
 
-				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
+				// TODO: fix below for mixed mono/stereo sources.
+				template <bool output_stereo>
+				void get_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
 					// Get the rest of the output.
 					next_source_.template get_samples<output_stereo>(number_of_samples, target);
 
@@ -72,7 +74,7 @@ template <typename... T> class CompoundSource:
 
 					// Get this component's output.
 					auto buffer_size = number_of_samples * (output_stereo ? 2 : 1);
-					int16_t local_samples[buffer_size];
+					typename SampleT<is_stereo>::type local_samples[number_of_samples];
 					source_.get_samples(number_of_samples, local_samples);
 
 					// Merge it in; furthermore if total output is stereo but this source isn't,
@@ -127,7 +129,7 @@ template <typename... T> class CompoundSource:
 			}
 		}
 
-		void get_samples(std::size_t number_of_samples, std::int16_t *target) {
+		void get_samples(std::size_t number_of_samples, typename SampleT<::Outputs::Speaker::is_stereo<T...>()>::type *target) {
 			source_holder_.template get_samples<::Outputs::Speaker::is_stereo<T...>()>(number_of_samples, target);
 		}
 
diff --git a/Outputs/Speaker/Speaker.hpp b/Outputs/Speaker/Speaker.hpp
index d65a54fc4..5195b4f77 100644
--- a/Outputs/Speaker/Speaker.hpp
+++ b/Outputs/Speaker/Speaker.hpp
@@ -14,13 +14,38 @@
 
 namespace Outputs::Speaker {
 
-template <bool stereo> struct SampleT;
-template <> struct SampleT<true> { using type = std::array<std::int16_t, 2>; };	// TODO: adopt left/right as per Dave?
-template <> struct SampleT<false> { using type = std::int16_t; };
-
 // Shorthands.
-using MonoSample = SampleT<false>::type;
-using StereoSample = SampleT<true>::type;
+using MonoSample = int16_t;
+struct StereoSample {
+#if TARGET_RT_BIG_ENDIAN
+	int16_t right, left;
+#else
+	int16_t left, right;
+#endif
+
+	StereoSample() = default;
+	StereoSample(const StereoSample &rhs) {
+		left = rhs.left;
+		right = rhs.right;
+	}
+
+	StereoSample &operator +=(const StereoSample &rhs) {
+		left += rhs.left;
+		right += rhs.right;
+		return *this;
+	}
+
+	StereoSample operator +(const StereoSample &rhs) {
+		StereoSample result;
+		result.left = left + rhs.left;
+		result.right = right + rhs.right;
+		return *this;
+	}
+};
+
+template <bool stereo> struct SampleT {
+	using type = std::conditional_t<stereo, StereoSample, MonoSample>;
+};
 
 /*!
 	Provides a communication point for sound; machines that have a speaker provide an

From 609d81d75d4d9bb386e3cabe016ef43cc2b4cdc7 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 9 Feb 2024 14:25:40 -0500
Subject: [PATCH 12/20] Distinguish sources of samples and of whole buffers.

---
 Components/6560/6560.hpp                      |  4 +-
 Components/AY38910/AY38910.hpp                |  4 +-
 Components/AudioToggle/AudioToggle.hpp        |  4 +-
 Components/KonamiSCC/KonamiSCC.hpp            |  4 +-
 Components/OPx/Implementation/OPLBase.hpp     |  4 +-
 Components/SN76489/SN76489.hpp                |  4 +-
 Machines/Apple/AppleIIgs/Sound.hpp            |  4 +-
 Machines/Apple/Macintosh/Audio.hpp            |  4 +-
 Machines/Atari/2600/TIASound.hpp              |  4 +-
 Machines/Electron/SoundGenerator.hpp          |  4 +-
 Machines/Enterprise/Dave.hpp                  |  4 +-
 Machines/MSX/MSX.cpp                          |  2 +-
 Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp   |  2 +-
 .../Clock Signal.xcodeproj/project.pbxproj    |  4 +-
 .../{SampleSource.hpp => BufferSource.hpp}    | 94 ++++++++++++++++---
 .../Speaker/Implementation/CompoundSource.hpp |  4 +-
 Outputs/Speaker/Speaker.hpp                   |  1 -
 17 files changed, 107 insertions(+), 44 deletions(-)
 rename Outputs/Speaker/Implementation/{SampleSource.hpp => BufferSource.hpp} (52%)

diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index 24d8e5479..a2535674e 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -12,12 +12,12 @@
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 #include "../../Outputs/CRT/CRT.hpp"
 #include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 
 namespace MOS::MOS6560 {
 
 // audio state
-class AudioGenerator: public Outputs::Speaker::SampleSource<AudioGenerator, false> {
+class AudioGenerator: public Outputs::Speaker::BufferSource<AudioGenerator, false> {
 	public:
 		AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index 58eb4ec80..2f30f61d9 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 
 #include "../../Reflection/Struct.hpp"
@@ -66,7 +66,7 @@ enum class Personality {
 
 	This AY has an attached mono or stereo mixer.
 */
-template <bool stereo> class AY38910: public ::Outputs::Speaker::SampleSource<AY38910<stereo>, stereo> {
+template <bool stereo> class AY38910: public ::Outputs::Speaker::BufferSource<AY38910<stereo>, stereo> {
 	public:
 		/// Creates a new AY38910.
 		AY38910(Personality, Concurrency::AsyncTaskQueue<false> &);
diff --git a/Components/AudioToggle/AudioToggle.hpp b/Components/AudioToggle/AudioToggle.hpp
index b93ea4cae..c8e962742 100644
--- a/Components/AudioToggle/AudioToggle.hpp
+++ b/Components/AudioToggle/AudioToggle.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 
 namespace Audio {
@@ -16,7 +16,7 @@ namespace Audio {
 /*!
 	Provides a sample source that can programmatically be set to one of two values.
 */
-class Toggle: public Outputs::Speaker::SampleSource<Toggle, false> {
+class Toggle: public Outputs::Speaker::BufferSource<Toggle, false> {
 	public:
 		Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Components/KonamiSCC/KonamiSCC.hpp b/Components/KonamiSCC/KonamiSCC.hpp
index 8d2986e85..7da684a73 100644
--- a/Components/KonamiSCC/KonamiSCC.hpp
+++ b/Components/KonamiSCC/KonamiSCC.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 
 namespace Konami {
@@ -20,7 +20,7 @@ namespace Konami {
 	and five channels of output. The original SCC uses the same wave for channels
 	four and five, the SCC+ supports different waves for the two channels.
 */
-class SCC: public ::Outputs::Speaker::SampleSource<SCC, false> {
+class SCC: public ::Outputs::Speaker::BufferSource<SCC, false> {
 	public:
 		/// Creates a new SCC.
 		SCC(Concurrency::AsyncTaskQueue<false> &task_queue);
diff --git a/Components/OPx/Implementation/OPLBase.hpp b/Components/OPx/Implementation/OPLBase.hpp
index 569e970a2..1890646a9 100644
--- a/Components/OPx/Implementation/OPLBase.hpp
+++ b/Components/OPx/Implementation/OPLBase.hpp
@@ -8,12 +8,12 @@
 
 #pragma once
 
-#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../../Concurrency/AsyncTaskQueue.hpp"
 
 namespace Yamaha::OPL {
 
-template <typename Child, bool stereo> class OPLBase: public ::Outputs::Speaker::SampleSource<Child, stereo> {
+template <typename Child, bool stereo> class OPLBase: public ::Outputs::Speaker::BufferSource<Child, stereo> {
 	public:
 		void write(uint16_t address, uint8_t value) {
 			if(address & 1) {
diff --git a/Components/SN76489/SN76489.hpp b/Components/SN76489/SN76489.hpp
index cab4469e1..ec35fb06b 100644
--- a/Components/SN76489/SN76489.hpp
+++ b/Components/SN76489/SN76489.hpp
@@ -8,12 +8,12 @@
 
 #pragma once
 
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 
 namespace TI {
 
-class SN76489: public Outputs::Speaker::SampleSource<SN76489, false> {
+class SN76489: public Outputs::Speaker::BufferSource<SN76489, false> {
 	public:
 		enum class Personality {
 			SN76489,
diff --git a/Machines/Apple/AppleIIgs/Sound.hpp b/Machines/Apple/AppleIIgs/Sound.hpp
index dece2832d..c65e9ceb9 100644
--- a/Machines/Apple/AppleIIgs/Sound.hpp
+++ b/Machines/Apple/AppleIIgs/Sound.hpp
@@ -12,11 +12,11 @@
 
 #include "../../../ClockReceiver/ClockReceiver.hpp"
 #include "../../../Concurrency/AsyncTaskQueue.hpp"
-#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"
 
 namespace Apple::IIgs::Sound {
 
-class GLU: public Outputs::Speaker::SampleSource<GLU, false> {	// TODO: isn't this stereo?
+class GLU: public Outputs::Speaker::BufferSource<GLU, false> {	// TODO: isn't this stereo?
 	public:
 		GLU(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index d7cbcaae0..09781c5fa 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -10,7 +10,7 @@
 
 #include "../../../Concurrency/AsyncTaskQueue.hpp"
 #include "../../../ClockReceiver/ClockReceiver.hpp"
-#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"
 
 #include <array>
 #include <atomic>
@@ -23,7 +23,7 @@ namespace Apple::Macintosh {
 	Designed to be clocked at half the rate of the real hardware — i.e.
 	a shade less than 4Mhz.
 */
-class Audio: public ::Outputs::Speaker::SampleSource<Audio, false> {
+class Audio: public ::Outputs::Speaker::BufferSource<Audio, false> {
 	public:
 		Audio(Concurrency::AsyncTaskQueue<false> &task_queue);
 
diff --git a/Machines/Atari/2600/TIASound.hpp b/Machines/Atari/2600/TIASound.hpp
index fdbbc3bfd..c1cace014 100644
--- a/Machines/Atari/2600/TIASound.hpp
+++ b/Machines/Atari/2600/TIASound.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../../Concurrency/AsyncTaskQueue.hpp"
 
 namespace Atari2600 {
@@ -17,7 +17,7 @@ namespace Atari2600 {
 // will give greater resolution to changes in audio state. 1, 2 and 19 are the only divisors of 38.
 constexpr int CPUTicksPerAudioTick = 2;
 
-class TIASound: public Outputs::Speaker::SampleSource<TIASound, false> {
+class TIASound: public Outputs::Speaker::BufferSource<TIASound, false> {
 	public:
 		TIASound(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Machines/Electron/SoundGenerator.hpp b/Machines/Electron/SoundGenerator.hpp
index 666c4c0c8..3222c68da 100644
--- a/Machines/Electron/SoundGenerator.hpp
+++ b/Machines/Electron/SoundGenerator.hpp
@@ -8,12 +8,12 @@
 
 #pragma once
 
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 
 namespace Electron {
 
-class SoundGenerator: public ::Outputs::Speaker::SampleSource<SoundGenerator, false> {
+class SoundGenerator: public ::Outputs::Speaker::BufferSource<SoundGenerator, false> {
 	public:
 		SoundGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index a3e369251..8e5b70622 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -13,7 +13,7 @@
 #include "../../ClockReceiver/ClockReceiver.hpp"
 #include "../../Concurrency/AsyncTaskQueue.hpp"
 #include "../../Numeric/LFSR.hpp"
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 
 namespace Enterprise::Dave {
 
@@ -26,7 +26,7 @@ enum class Interrupt: uint8_t {
 /*!
 	Models the audio-production subset of Dave's behaviour.
 */
-class Audio: public Outputs::Speaker::SampleSource<Audio, true> {
+class Audio: public Outputs::Speaker::BufferSource<Audio, true> {
 	public:
 		Audio(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
diff --git a/Machines/MSX/MSX.cpp b/Machines/MSX/MSX.cpp
index 8d3ea168d..f4e02b8f2 100644
--- a/Machines/MSX/MSX.cpp
+++ b/Machines/MSX/MSX.cpp
@@ -41,7 +41,7 @@
 #include "../../Outputs/Log.hpp"
 #include "../../Outputs/Speaker/Implementation/CompoundSource.hpp"
 #include "../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
-#include "../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../Outputs/Speaker/Implementation/BufferSource.hpp"
 
 #include "../../Configurable/StandardOptions.hpp"
 #include "../../ClockReceiver/ForceInline.hpp"
diff --git a/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp b/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
index 62406a629..c20e43fff 100644
--- a/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
+++ b/Machines/Sinclair/ZXSpectrum/ZXSpectrum.cpp
@@ -28,7 +28,7 @@
 
 #include "../../../Outputs/Speaker/Implementation/CompoundSource.hpp"
 #include "../../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
-#include "../../../Outputs/Speaker/Implementation/SampleSource.hpp"
+#include "../../../Outputs/Speaker/Implementation/BufferSource.hpp"
 
 #include "../../../Storage/Tape/Tape.hpp"
 #include "../../../Storage/Tape/Parsers/Spectrum.hpp"
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 09dd756a7..3babbde3e 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -1533,7 +1533,7 @@
 		4B680CE123A5553100451D43 /* 68000ComparativeTests.mm */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.objcpp; path = 68000ComparativeTests.mm; sourceTree = "<group>"; };
 		4B680CE323A555CA00451D43 /* 68000 Comparative Tests */ = {isa = PBXFileReference; lastKnownFileType = folder; path = "68000 Comparative Tests"; sourceTree = "<group>"; };
 		4B683B002727BE6F0043E541 /* Amiga Blitter Tests */ = {isa = PBXFileReference; lastKnownFileType = folder; path = "Amiga Blitter Tests"; sourceTree = "<group>"; };
-		4B698D1A1FE768A100696C91 /* SampleSource.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = SampleSource.hpp; sourceTree = "<group>"; };
+		4B698D1A1FE768A100696C91 /* BufferSource.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = BufferSource.hpp; sourceTree = "<group>"; };
 		4B69DEB52AB79E4F0055B217 /* Instruction.cpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.cpp; path = Instruction.cpp; sourceTree = "<group>"; };
 		4B69FB3B1C4D908A00B5F0AA /* Tape.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = Tape.cpp; sourceTree = "<group>"; };
 		4B69FB3C1C4D908A00B5F0AA /* Tape.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = Tape.hpp; sourceTree = "<group>"; };
@@ -4004,7 +4004,7 @@
 			isa = PBXGroup;
 			children = (
 				4B8EF6071FE5AF830076CCDD /* LowpassSpeaker.hpp */,
-				4B698D1A1FE768A100696C91 /* SampleSource.hpp */,
+				4B698D1A1FE768A100696C91 /* BufferSource.hpp */,
 				4B770A961FE9EE770026DC70 /* CompoundSource.hpp */,
 			);
 			path = Implementation;
diff --git a/Outputs/Speaker/Implementation/SampleSource.hpp b/Outputs/Speaker/Implementation/BufferSource.hpp
similarity index 52%
rename from Outputs/Speaker/Implementation/SampleSource.hpp
rename to Outputs/Speaker/Implementation/BufferSource.hpp
index 36afe40f7..e212e2ef8 100644
--- a/Outputs/Speaker/Implementation/SampleSource.hpp
+++ b/Outputs/Speaker/Implementation/BufferSource.hpp
@@ -22,7 +22,7 @@ namespace Outputs::Speaker {
 	by the template parameter to LowpassSpeaker.
 */
 template <typename SourceT, bool stereo>
-class SampleSource {
+class BufferSource {
 	public:
 		/*!
 			Indicates whether this component will write stereo samples.
@@ -32,13 +32,7 @@ class SampleSource {
 		/*!
 			Should write the next @c number_of_samples to @c target.
 		*/
-		void get_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target) {
-			const auto &source = *static_cast<SourceT *>(this);
-			while(number_of_samples--) {
-				*target = source.level();
-				++target;
-			}
-		}
+		void get_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] typename SampleT<stereo>::type *target) {}
 
 		/*!
 			Should skip the next @c number_of_samples. Subclasses of this SampleSource
@@ -46,10 +40,7 @@ class SampleSource {
 			merely to call get_samples and throw the result away, as per the default
 			implementation below.
 		*/
-		void skip_samples(const std::size_t number_of_samples) {
-			if constexpr (&SourceT::advance == &SampleSource<SourceT, stereo>::advance) {
-				return;
-			}
+		void skip_samples(std::size_t number_of_samples) {
 			typename SampleT<stereo>::type scratch_pad[number_of_samples];
 			get_samples(number_of_samples, scratch_pad);
 		}
@@ -59,9 +50,7 @@ class SampleSource {
 				fill the target with zeroes; @c false if a call might return all zeroes or
 				might not.
 		*/
-		bool is_zero_level() const						{	return false;					}
-		auto level() const								{	return typename SampleT<stereo>::type();	}
-		void advance()									{}
+		bool is_zero_level() const						{	return false;	}
 
 		/*!
 			Sets the proper output range for this sample source; it should write values
@@ -82,4 +71,79 @@ class SampleSource {
 		double average_output_peak() const { return 1.0; }
 };
 
+///
+template <typename SourceT, bool stereo, int divider = 1>
+struct SampleSource: public BufferSource<SourceT, stereo> {
+	public:
+		void get_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target) {
+			const auto &source = *static_cast<SourceT *>(this);
+
+			if constexpr (divider == 1) {
+				while(number_of_samples--) {
+					*target = source.level();
+					++target;
+				}
+			} else {
+				std::size_t c = 0;
+
+				// Fill in the tail of any pa3rtially-captured level.
+				auto level = source.level();
+				while(c < number_of_samples && master_divider_ != divider) {
+					target[c] = level;
+					++c;
+					++master_divider_;
+				}
+				source.advance();
+
+				// Provide all full levels.
+				int whole_steps = (number_of_samples - c) / divider;
+				while(whole_steps--) {
+					std::fill(&target[c], &target[c + divider], source.level());
+					c += divider;
+					source.advance();
+				}
+
+				// Provide the head of a further partial capture.
+				level = source.level();
+				master_divider_ = number_of_samples - c;
+				std::fill(&target[c], &target[number_of_samples], source.level());
+			}
+		}
+
+		void skip_samples(std::size_t number_of_samples) {
+			const auto &source = *static_cast<SourceT *>(this);
+
+			if constexpr (&SourceT::advance == &SampleSource::advance) {
+				return;
+			}
+
+			if constexpr (divider == 1) {
+				while(--number_of_samples) {
+					source.advance();
+				}
+			} else {
+				if(number_of_samples >= divider - master_divider_) {
+					source.advance();
+					number_of_samples -= (divider - master_divider_);
+				}
+				while(number_of_samples > divider) {
+					advance();
+					number_of_samples -= divider;
+				}
+				master_divider_ = number_of_samples;
+			}
+		}
+
+		// TODO: use a concept here, when C++20 filters through.
+		//
+		// Until then: sample sources should implement this.
+		auto level() const	{
+			return typename SampleT<stereo>::type();
+		}
+		void advance() {}
+
+	private:
+		int master_divider_{};
+};
+
 }
diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 16d33657f..6bc77220a 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -8,7 +8,7 @@
 
 #pragma once
 
-#include "SampleSource.hpp"
+#include "BufferSource.hpp"
 
 #include <algorithm>
 #include <cassert>
@@ -31,7 +31,7 @@ template <typename... S> constexpr bool is_stereo() {
 	An owner may optionally assign relative volumes.
 */
 template <typename... T> class CompoundSource:
-	public Outputs::Speaker::SampleSource<CompoundSource<T...>, ::Outputs::Speaker::is_stereo<T...>()> {
+	public Outputs::Speaker::BufferSource<CompoundSource<T...>, ::Outputs::Speaker::is_stereo<T...>()> {
 	private:
 		template <typename... S> class CompoundSourceHolder {
 			public:
diff --git a/Outputs/Speaker/Speaker.hpp b/Outputs/Speaker/Speaker.hpp
index 5195b4f77..9bbb91821 100644
--- a/Outputs/Speaker/Speaker.hpp
+++ b/Outputs/Speaker/Speaker.hpp
@@ -14,7 +14,6 @@
 
 namespace Outputs::Speaker {
 
-// Shorthands.
 using MonoSample = int16_t;
 struct StereoSample {
 #if TARGET_RT_BIG_ENDIAN

From 9909146c599541ce463c45cfc9eedad50b91931f Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 9 Feb 2024 14:26:02 -0500
Subject: [PATCH 13/20] Fix typo.

---
 Outputs/Speaker/Implementation/BufferSource.hpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/Outputs/Speaker/Implementation/BufferSource.hpp b/Outputs/Speaker/Implementation/BufferSource.hpp
index e212e2ef8..f493ea338 100644
--- a/Outputs/Speaker/Implementation/BufferSource.hpp
+++ b/Outputs/Speaker/Implementation/BufferSource.hpp
@@ -86,7 +86,7 @@ struct SampleSource: public BufferSource<SourceT, stereo> {
 			} else {
 				std::size_t c = 0;
 
-				// Fill in the tail of any pa3rtially-captured level.
+				// Fill in the tail of any partially-captured level.
 				auto level = source.level();
 				while(c < number_of_samples && master_divider_ != divider) {
 					target[c] = level;

From 25085cb5afc470d9119273940f242a3e824e80cd Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Fri, 9 Feb 2024 14:34:59 -0500
Subject: [PATCH 14/20] Require good ordering.

---
 .../Speaker/Implementation/CompoundSource.hpp | 19 ++++++++++++++++++-
 1 file changed, 18 insertions(+), 1 deletion(-)

diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index 6bc77220a..a4a9f2251 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -26,6 +26,20 @@ template <typename... S> constexpr bool is_stereo() {
 	return is_stereo;
 }
 
+/// @returns @c true if the variadic template arguments are ordered as all stereo sources followed by
+/// all mono; @c false otherwise.
+template <typename... S> constexpr bool are_properly_ordered() {
+	bool is_ordered = true;
+	bool is_stereo = true;
+	([&] {
+		if(S::is_stereo && !is_stereo) {
+			is_ordered = false;
+		}
+		is_stereo &= S::is_stereo;
+	}(), ...);
+	return is_ordered;
+}
+
 /*!
 	A CompoundSource adds together the sound generated by multiple individual SampleSources.
 	An owner may optionally assign relative volumes.
@@ -59,7 +73,7 @@ template <typename... T> class CompoundSource:
 
 				static constexpr bool is_stereo = S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
 
-				// TODO: fix below for mixed mono/stereo sources.
+				// TODO: fix below for potential stereo -> mono conversion.
 				template <bool output_stereo>
 				void get_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
 					// Get the rest of the output.
@@ -121,6 +135,9 @@ template <typename... T> class CompoundSource:
 		};
 
 	public:
+		// To ensure at most one mono to stereo conversion, require appropriate source ordering.
+		static_assert(are_properly_ordered<T...>(), "Sources should be listed with all stereo sources before all mono sources");
+
 		CompoundSource(T &... sources) : source_holder_(sources...) {
 			// Default: give all sources equal volume.
 			const auto volume = 1.0 / double(source_holder_.size());

From 3a208460e28ce1d579e382f663bf3f715580a281 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Sat, 10 Feb 2024 21:53:12 -0500
Subject: [PATCH 15/20] Reintroduce mono to stereo conversion.

---
 .../Speaker/Implementation/CompoundSource.hpp | 53 +++++++++++--------
 Outputs/Speaker/Speaker.hpp                   |  4 +-
 2 files changed, 34 insertions(+), 23 deletions(-)

diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index a4a9f2251..cfdf3d962 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -49,8 +49,10 @@ template <typename... T> class CompoundSource:
 	private:
 		template <typename... S> class CompoundSourceHolder {
 			public:
-				template <bool output_stereo> void get_samples(std::size_t number_of_samples, std::int16_t *target) {
-					std::fill(target, target + number_of_samples, 0);
+				template <bool output_stereo>
+				void get_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
+					// Default-construct all samples, to fill with silence.
+					std::fill(target, target + number_of_samples, typename SampleT<output_stereo>::type());
 				}
 
 				void set_scaled_volume_range(int16_t, double *, double) {}
@@ -73,9 +75,27 @@ template <typename... T> class CompoundSource:
 
 				static constexpr bool is_stereo = S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
 
-				// TODO: fix below for potential stereo -> mono conversion.
 				template <bool output_stereo>
-				void get_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
+				void get_samples(std::size_t number_of_samples, typename ::Outputs::Speaker::SampleT<output_stereo>::type *target) {
+
+					// If this is the step at which a mono-to-stereo adaptation happens, apply it.
+					if constexpr (output_stereo && !S::is_stereo) {
+						// There'll be only one place in the chain that this conversion happens, but it'll
+						// happen there often. So avoid continuously reallocating.
+						if(conversion_source_.size() < number_of_samples) {
+							conversion_source_.resize(number_of_samples);
+						}
+
+						// Populate the conversion buffer with this source and all below.
+						get_samples<false>(number_of_samples, conversion_source_.data());
+
+						// Map up and return.
+						for(std::size_t c = 0; c < number_of_samples; c++) {
+							target[c].left = target[c].right = conversion_source_[c];
+						}
+						return;
+					}
+
 					// Get the rest of the output.
 					next_source_.template get_samples<output_stereo>(number_of_samples, target);
 
@@ -87,24 +107,12 @@ template <typename... T> class CompoundSource:
 					}
 
 					// Get this component's output.
-					auto buffer_size = number_of_samples * (output_stereo ? 2 : 1);
-					typename SampleT<is_stereo>::type local_samples[number_of_samples];
+					typename SampleT<output_stereo>::type local_samples[number_of_samples];
 					source_.get_samples(number_of_samples, local_samples);
 
-					// Merge it in; furthermore if total output is stereo but this source isn't,
-					// map it to stereo.
-					if constexpr (output_stereo == S::is_stereo) {
-						while(buffer_size--) {
-							target[buffer_size] += local_samples[buffer_size];
-						}
-					} else {
-						// This will happen only if mapping from mono to stereo, never in the
-						// other direction, because the compound source outputs stereo if any
-						// subcomponent does. So it outputs mono only if no stereo devices are
-						// in the mixing chain.
-						while(buffer_size--) {
-							target[buffer_size] += local_samples[buffer_size >> 1];
-						}
+					// Merge it in.
+					while(number_of_samples--) {
+						target[number_of_samples] += local_samples[number_of_samples];
 					}
 
 					// TODO: accelerate above?
@@ -132,9 +140,12 @@ template <typename... T> class CompoundSource:
 			private:
 				S &source_;
 				CompoundSourceHolder<R...> next_source_;
+				std::vector<MonoSample> conversion_source_;
 		};
 
 	public:
+		using Sample = typename SampleT<::Outputs::Speaker::is_stereo<T...>()>::type;
+
 		// To ensure at most one mono to stereo conversion, require appropriate source ordering.
 		static_assert(are_properly_ordered<T...>(), "Sources should be listed with all stereo sources before all mono sources");
 
@@ -146,7 +157,7 @@ template <typename... T> class CompoundSource:
 			}
 		}
 
-		void get_samples(std::size_t number_of_samples, typename SampleT<::Outputs::Speaker::is_stereo<T...>()>::type *target) {
+		void get_samples(std::size_t number_of_samples, Sample *target) {
 			source_holder_.template get_samples<::Outputs::Speaker::is_stereo<T...>()>(number_of_samples, target);
 		}
 
diff --git a/Outputs/Speaker/Speaker.hpp b/Outputs/Speaker/Speaker.hpp
index 9bbb91821..860395536 100644
--- a/Outputs/Speaker/Speaker.hpp
+++ b/Outputs/Speaker/Speaker.hpp
@@ -17,9 +17,9 @@ namespace Outputs::Speaker {
 using MonoSample = int16_t;
 struct StereoSample {
 #if TARGET_RT_BIG_ENDIAN
-	int16_t right, left;
+	int16_t right = 0, left = 0;
 #else
-	int16_t left, right;
+	int16_t left = 0, right = 0;
 #endif
 
 	StereoSample() = default;

From d49c07687c2f5b590623eb34a242e45c4182324d Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Feb 2024 10:55:52 -0500
Subject: [PATCH 16/20] Unify [get_/skip_]samples, adding a third option for
 in-place mixing.

---
 Components/6560/6560.cpp                      | 25 +++---
 Components/6560/6560.hpp                      |  5 +-
 Components/AY38910/AY38910.cpp                | 14 ++-
 Components/AY38910/AY38910.hpp                |  5 +-
 Components/AudioToggle/AudioToggle.cpp        |  6 --
 Components/AudioToggle/AudioToggle.hpp        |  6 +-
 Components/KonamiSCC/KonamiSCC.cpp            | 14 +--
 Components/KonamiSCC/KonamiSCC.hpp            |  5 +-
 Components/OPx/OPLL.cpp                       |  9 +-
 Components/OPx/OPLL.hpp                       |  3 +-
 Components/SN76489/SN76489.cpp                | 10 ++-
 Components/SN76489/SN76489.hpp                |  3 +-
 Machines/Apple/AppleIIgs/Sound.cpp            | 53 +++++++-----
 Machines/Apple/AppleIIgs/Sound.hpp            |  7 +-
 Machines/Apple/Macintosh/Audio.cpp            |  8 +-
 Machines/Apple/Macintosh/Audio.hpp            |  3 +-
 Machines/Atari/2600/TIASound.cpp              | 11 ++-
 Machines/Atari/2600/TIASound.hpp              |  3 +-
 Machines/Electron/SoundGenerator.cpp          | 19 ++--
 Machines/Electron/SoundGenerator.hpp          |  4 +-
 Machines/Enterprise/Dave.cpp                  |  8 +-
 Machines/Enterprise/Dave.hpp                  |  3 +-
 .../xcschemes/Clock Signal.xcscheme           |  2 +-
 .../Speaker/Implementation/BufferSource.hpp   | 86 ++++++++++---------
 .../Speaker/Implementation/CompoundSource.hpp | 44 +++-------
 .../Speaker/Implementation/LowpassSpeaker.hpp |  7 +-
 Outputs/Speaker/Speaker.hpp                   |  3 +
 27 files changed, 204 insertions(+), 162 deletions(-)

diff --git a/Components/6560/6560.cpp b/Components/6560/6560.cpp
index 3ca2b145f..51d053994 100644
--- a/Components/6560/6560.cpp
+++ b/Components/6560/6560.cpp
@@ -19,6 +19,7 @@ AudioGenerator::AudioGenerator(Concurrency::AsyncTaskQueue<false> &audio_queue)
 void AudioGenerator::set_volume(uint8_t volume) {
 	audio_queue_.enqueue([this, volume]() {
 		volume_ = int16_t(volume) * range_multiplier_;
+		dc_offset_ = volume_ >> 4;
 	});
 }
 
@@ -105,7 +106,8 @@ static uint8_t noise_pattern[] = {
 // testing against 0x80. The effect should be the same: loading with 0x7f means an output update every cycle, loading with 0x7e
 // means every second cycle, etc.
 
-void AudioGenerator::get_samples(std::size_t number_of_samples, int16_t *target) {
+template <Outputs::Speaker::Action action>
+void AudioGenerator::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	for(unsigned int c = 0; c < number_of_samples; ++c) {
 		update(0, 2, shift);
 		update(1, 1, shift);
@@ -114,23 +116,22 @@ void AudioGenerator::get_samples(std::size_t number_of_samples, int16_t *target)
 
 		// this sums the output of all three sounds channels plus a DC offset for volume;
 		// TODO: what's the real ratio of this stuff?
-		target[c] = int16_t(
+		const int16_t sample =
 			(shift_registers_[0]&1) +
 			(shift_registers_[1]&1) +
 			(shift_registers_[2]&1) +
-			((noise_pattern[shift_registers_[3] >> 3] >> (shift_registers_[3]&7))&(control_registers_[3] >> 7)&1)
-		) * volume_ + (volume_ >> 4);
-	}
-}
+			((noise_pattern[shift_registers_[3] >> 3] >> (shift_registers_[3]&7))&(control_registers_[3] >> 7)&1);
 
-void AudioGenerator::skip_samples(std::size_t number_of_samples) {
-	for(unsigned int c = 0; c < number_of_samples; ++c) {
-		update(0, 2, shift);
-		update(1, 1, shift);
-		update(2, 0, shift);
-		update(3, 1, increment);
+		Outputs::Speaker::apply<action>(
+			target[c],
+			Outputs::Speaker::MonoSample(
+				sample * volume_ + dc_offset_
+			));
 	}
 }
+template void AudioGenerator::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void AudioGenerator::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void AudioGenerator::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
 
 void AudioGenerator::set_sample_volume_range(std::int16_t range) {
 	range_multiplier_ = int16_t(range / 64);
diff --git a/Components/6560/6560.hpp b/Components/6560/6560.hpp
index a2535674e..e87580fad 100644
--- a/Components/6560/6560.hpp
+++ b/Components/6560/6560.hpp
@@ -25,8 +25,8 @@ class AudioGenerator: public Outputs::Speaker::BufferSource<AudioGenerator, fals
 		void set_control(int channel, uint8_t value);
 
 		// For ::SampleSource.
-		void get_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
-		void skip_samples(std::size_t number_of_samples);
+		template <Outputs::Speaker::Action action>
+			void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
 
 	private:
@@ -36,6 +36,7 @@ class AudioGenerator: public Outputs::Speaker::BufferSource<AudioGenerator, fals
 		unsigned int shift_registers_[4] = {0, 0, 0, 0};
 		uint8_t control_registers_[4] = {0, 0, 0, 0};
 		int16_t volume_ = 0;
+		int16_t dc_offset_ = 0;
 		int16_t range_multiplier_ = 1;
 };
 
diff --git a/Components/AY38910/AY38910.cpp b/Components/AY38910/AY38910.cpp
index e2ad41467..4bf37fafa 100644
--- a/Components/AY38910/AY38910.cpp
+++ b/Components/AY38910/AY38910.cpp
@@ -102,7 +102,8 @@ template <bool is_stereo> void AY38910<is_stereo>::set_output_mixing(float a_lef
 }
 
 template <bool is_stereo>
-void AY38910<is_stereo>::get_samples(
+template <Outputs::Speaker::Action action>
+void AY38910<is_stereo>::apply_samples(
 	std::size_t number_of_samples,
 	typename Outputs::Speaker::SampleT<is_stereo>::type *target
 ) {
@@ -117,7 +118,7 @@ void AY38910<is_stereo>::get_samples(
 
 	std::size_t c = 0;
 	while((master_divider_&3) && c < number_of_samples) {
-		target[c] = output_volume_;
+		Outputs::Speaker::apply<action>(target[c], output_volume_);
 		master_divider_++;
 		c++;
 	}
@@ -159,7 +160,7 @@ void AY38910<is_stereo>::get_samples(
 		evaluate_output_volume();
 
 		for(int ic = 0; ic < 4 && c < number_of_samples; ic++) {
-			target[c] = output_volume_;
+			Outputs::Speaker::apply<action>(target[c], output_volume_);
 			c++;
 			master_divider_++;
 		}
@@ -168,6 +169,13 @@ void AY38910<is_stereo>::get_samples(
 	master_divider_ &= 3;
 }
 
+template void AY38910<false>::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, typename Outputs::Speaker::SampleT<false>::type *);
+template void AY38910<false>::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, typename Outputs::Speaker::SampleT<false>::type *);
+template void AY38910<false>::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, typename Outputs::Speaker::SampleT<false>::type *);
+template void AY38910<true>::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, typename Outputs::Speaker::SampleT<true>::type *);
+template void AY38910<true>::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, typename Outputs::Speaker::SampleT<true>::type *);
+template void AY38910<true>::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, typename Outputs::Speaker::SampleT<true>::type *);
+
 template <bool is_stereo> void AY38910<is_stereo>::evaluate_output_volume() {
 	int envelope_volume = envelope_shapes_[output_registers_[13]][envelope_position_ | envelope_position_mask_];
 
diff --git a/Components/AY38910/AY38910.hpp b/Components/AY38910/AY38910.hpp
index 2f30f61d9..722abcba2 100644
--- a/Components/AY38910/AY38910.hpp
+++ b/Components/AY38910/AY38910.hpp
@@ -105,8 +105,9 @@ template <bool stereo> class AY38910: public ::Outputs::Speaker::BufferSource<AY
 		*/
 		void set_output_mixing(float a_left, float b_left, float c_left, float a_right = 1.0, float b_right = 1.0, float c_right = 1.0);
 
-		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter.
-		void get_samples(std::size_t number_of_samples, typename Outputs::Speaker::SampleT<stereo>::type *target);
+		// Buffer generation.
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, typename Outputs::Speaker::SampleT<stereo>::type *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
 
diff --git a/Components/AudioToggle/AudioToggle.cpp b/Components/AudioToggle/AudioToggle.cpp
index ee8e2b417..77c329972 100644
--- a/Components/AudioToggle/AudioToggle.cpp
+++ b/Components/AudioToggle/AudioToggle.cpp
@@ -15,17 +15,11 @@ using namespace Audio;
 Audio::Toggle::Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue) :
 	audio_queue_(audio_queue) {}
 
-void Toggle::get_samples(std::size_t number_of_samples, std::int16_t *target) {
-	std::fill(target, target + number_of_samples, level_);
-}
-
 void Toggle::set_sample_volume_range(std::int16_t range) {
 	volume_ = range;
 	level_ = level_active_ ? volume_ : 0;
 }
 
-void Toggle::skip_samples(std::size_t) {}
-
 void Toggle::set_output(bool enabled) {
 	if(is_enabled_ == enabled) return;
 	is_enabled_ = enabled;
diff --git a/Components/AudioToggle/AudioToggle.hpp b/Components/AudioToggle/AudioToggle.hpp
index c8e962742..ea304e06a 100644
--- a/Components/AudioToggle/AudioToggle.hpp
+++ b/Components/AudioToggle/AudioToggle.hpp
@@ -20,9 +20,11 @@ class Toggle: public Outputs::Speaker::BufferSource<Toggle, false> {
 	public:
 		Toggle(Concurrency::AsyncTaskQueue<false> &audio_queue);
 
-		void get_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
+			Outputs::Speaker::fill<action>(target, target + number_of_samples, level_);
+		}
 		void set_sample_volume_range(std::int16_t range);
-		void skip_samples(const std::size_t number_of_samples);
 
 		void set_output(bool enabled);
 		bool get_output() const;
diff --git a/Components/KonamiSCC/KonamiSCC.cpp b/Components/KonamiSCC/KonamiSCC.cpp
index 81a2af502..c4c1abc8d 100644
--- a/Components/KonamiSCC/KonamiSCC.cpp
+++ b/Components/KonamiSCC/KonamiSCC.cpp
@@ -19,15 +19,16 @@ bool SCC::is_zero_level() const {
 	return !(channel_enable_ & 0x1f);
 }
 
-void SCC::get_samples(std::size_t number_of_samples, std::int16_t *target) {
+template <Outputs::Speaker::Action action>
+void SCC::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	if(is_zero_level()) {
-		std::memset(target, 0, sizeof(std::int16_t) * number_of_samples);
+		Outputs::Speaker::fill<action>(target, target + number_of_samples, Outputs::Speaker::MonoSample());
 		return;
 	}
 
 	std::size_t c = 0;
 	while((master_divider_&7) && c < number_of_samples) {
-		target[c] = transient_output_level_;
+		Outputs::Speaker::apply<action>(target[c], transient_output_level_);
 		master_divider_++;
 		c++;
 	}
@@ -44,12 +45,15 @@ void SCC::get_samples(std::size_t number_of_samples, std::int16_t *target) {
 		evaluate_output_volume();
 
 		for(int ic = 0; ic < 8 && c < number_of_samples; ++ic) {
-			target[c] = transient_output_level_;
+			Outputs::Speaker::apply<action>(target[c], transient_output_level_);
 			c++;
 			master_divider_++;
 		}
 	}
 }
+template void SCC::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void SCC::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void SCC::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
 
 void SCC::write(uint16_t address, uint8_t value) {
 	address &= 0xff;
@@ -111,5 +115,3 @@ uint8_t SCC::read(uint16_t address) {
 	}
 	return 0xff;
 }
-
-
diff --git a/Components/KonamiSCC/KonamiSCC.hpp b/Components/KonamiSCC/KonamiSCC.hpp
index 7da684a73..5a379c3d0 100644
--- a/Components/KonamiSCC/KonamiSCC.hpp
+++ b/Components/KonamiSCC/KonamiSCC.hpp
@@ -29,7 +29,8 @@ class SCC: public ::Outputs::Speaker::BufferSource<SCC, false> {
 		bool is_zero_level() const;
 
 		/// As per ::SampleSource; provides audio output.
-		void get_samples(std::size_t number_of_samples, std::int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
 
 		/// Writes to the SCC.
@@ -44,7 +45,7 @@ class SCC: public ::Outputs::Speaker::BufferSource<SCC, false> {
 		// State from here on down is accessed ony from the audio thread.
 		int master_divider_ = 0;
 		std::int16_t master_volume_ = 0;
-		int16_t transient_output_level_ = 0;
+		Outputs::Speaker::MonoSample transient_output_level_ = 0;
 
 		struct Channel {
 			int period = 0;
diff --git a/Components/OPx/OPLL.cpp b/Components/OPx/OPLL.cpp
index f5d8feddd..b1bb81935 100644
--- a/Components/OPx/OPLL.cpp
+++ b/Components/OPx/OPLL.cpp
@@ -278,7 +278,8 @@ void OPLL::set_sample_volume_range(std::int16_t range) {
 	total_volume_ = range;
 }
 
-void OPLL::get_samples(std::size_t number_of_samples, std::int16_t *target) {
+template <Outputs::Speaker::Action action>
+void OPLL::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	// Both the OPLL and the OPL2 divide the input clock by 72 to get the base tick frequency;
 	// unlike the OPL2 the OPLL time-divides the output for 'mixing'.
 
@@ -289,12 +290,16 @@ void OPLL::get_samples(std::size_t number_of_samples, std::int16_t *target) {
 	while(number_of_samples--) {
 		if(!audio_offset_) update_all_channels();
 
-		*target = output_levels_[audio_offset_ / channel_output_period];
+		Outputs::Speaker::apply<action>(*target, output_levels_[audio_offset_ / channel_output_period]);
 		++target;
 		audio_offset_ = (audio_offset_ + 1) % update_period;
 	}
 }
 
+template void OPLL::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void OPLL::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void OPLL::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
+
 void OPLL::update_all_channels() {
 	oscillator_.update();
 
diff --git a/Components/OPx/OPLL.hpp b/Components/OPx/OPLL.hpp
index 8d35e8e1b..da08a3f97 100644
--- a/Components/OPx/OPLL.hpp
+++ b/Components/OPx/OPLL.hpp
@@ -25,7 +25,8 @@ class OPLL: public OPLBase<OPLL, false> {
 		OPLL(Concurrency::AsyncTaskQueue<false> &task_queue, int audio_divider = 1, bool is_vrc7 = false);
 
 		/// As per ::SampleSource; provides audio output.
-		void get_samples(std::size_t number_of_samples, std::int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
 
 		// The OPLL is generally 'half' as loud as it's told to be. This won't strictly be true in
diff --git a/Components/SN76489/SN76489.cpp b/Components/SN76489/SN76489.cpp
index 8705b24c7..007df3516 100644
--- a/Components/SN76489/SN76489.cpp
+++ b/Components/SN76489/SN76489.cpp
@@ -99,10 +99,11 @@ void SN76489::evaluate_output_volume() {
 	);
 }
 
-void SN76489::get_samples(std::size_t number_of_samples, std::int16_t *target) {
+template <Outputs::Speaker::Action action>
+void SN76489::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	std::size_t c = 0;
 	while((master_divider_& (master_divider_period_ - 1)) && c < number_of_samples) {
-		target[c] = output_volume_;
+		Outputs::Speaker::apply<action>(target[c], output_volume_);
 		master_divider_++;
 		c++;
 	}
@@ -151,7 +152,7 @@ void SN76489::get_samples(std::size_t number_of_samples, std::int16_t *target) {
 		evaluate_output_volume();
 
 		for(int ic = 0; ic < master_divider_period_ && c < number_of_samples; ++ic) {
-			target[c] = output_volume_;
+			Outputs::Speaker::apply<action>(target[c], output_volume_);
 			c++;
 			master_divider_++;
 		}
@@ -159,3 +160,6 @@ void SN76489::get_samples(std::size_t number_of_samples, std::int16_t *target) {
 
 	master_divider_ &= (master_divider_period_ - 1);
 }
+template void SN76489::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void SN76489::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void SN76489::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
diff --git a/Components/SN76489/SN76489.hpp b/Components/SN76489/SN76489.hpp
index ec35fb06b..5e79e3e83 100644
--- a/Components/SN76489/SN76489.hpp
+++ b/Components/SN76489/SN76489.hpp
@@ -28,7 +28,8 @@ class SN76489: public Outputs::Speaker::BufferSource<SN76489, false> {
 		void write(uint8_t value);
 
 		// As per SampleSource.
-		void get_samples(std::size_t number_of_samples, std::int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
 
diff --git a/Machines/Apple/AppleIIgs/Sound.cpp b/Machines/Apple/AppleIIgs/Sound.cpp
index 0a5c78869..d52d6f3e3 100644
--- a/Machines/Apple/AppleIIgs/Sound.cpp
+++ b/Machines/Apple/AppleIIgs/Sound.cpp
@@ -159,29 +159,34 @@ void GLU::run_for(Cycles cycles) {
 	pending_store_write_time_ += cycles.as<uint32_t>();
 }
 
-void GLU::get_samples(std::size_t number_of_samples, std::int16_t *target) {
+template <Outputs::Speaker::Action action>
+void GLU::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	// Update remote state, generating audio.
-	generate_audio(number_of_samples, target);
+	generate_audio<action>(number_of_samples, target);
 }
+template void GLU::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void GLU::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void GLU::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
 
-void GLU::skip_samples(const std::size_t number_of_samples) {
-	// Update remote state, without generating audio.
-	skip_audio(remote_, number_of_samples);
 
-	// Apply any pending stores.
-	std::atomic_thread_fence(std::memory_order::memory_order_acquire);
-	const uint32_t final_time = pending_store_read_time_ + uint32_t(number_of_samples);
-	while(true) {
-		auto next_store = pending_stores_[pending_store_read_].load(std::memory_order::memory_order_acquire);
-		if(!next_store.enabled) break;
-		if(next_store.time >= final_time) break;
-		remote_.ram_[next_store.address] = next_store.value;
-		next_store.enabled = false;
-		pending_stores_[pending_store_read_].store(next_store, std::memory_order::memory_order_relaxed);
-
-		pending_store_read_ = (pending_store_read_ + 1) & (StoreBufferSize - 1);
-	}
-}
+//void GLU::skip_samples(const std::size_t number_of_samples) {
+//	// Update remote state, without generating audio.
+//	skip_audio(remote_, number_of_samples);
+//
+//	// Apply any pending stores.
+//	std::atomic_thread_fence(std::memory_order::memory_order_acquire);
+//	const uint32_t final_time = pending_store_read_time_ + uint32_t(number_of_samples);
+//	while(true) {
+//		auto next_store = pending_stores_[pending_store_read_].load(std::memory_order::memory_order_acquire);
+//		if(!next_store.enabled) break;
+//		if(next_store.time >= final_time) break;
+//		remote_.ram_[next_store.address] = next_store.value;
+//		next_store.enabled = false;
+//		pending_stores_[pending_store_read_].store(next_store, std::memory_order::memory_order_relaxed);
+//
+//		pending_store_read_ = (pending_store_read_ + 1) & (StoreBufferSize - 1);
+//	}
+//}
 
 void GLU::set_sample_volume_range(std::int16_t range) {
 	output_range_ = range;
@@ -256,7 +261,8 @@ void GLU::skip_audio(EnsoniqState &state, size_t number_of_samples) {
 	}
 }
 
-void GLU::generate_audio(size_t number_of_samples, std::int16_t *target) {
+template <Outputs::Speaker::Action action>
+void GLU::generate_audio(size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	auto next_store = pending_stores_[pending_store_read_].load(std::memory_order::memory_order_acquire);
 	uint8_t next_amplitude = 255;
 	for(size_t sample = 0; sample < number_of_samples; sample++) {
@@ -325,7 +331,12 @@ void GLU::generate_audio(size_t number_of_samples, std::int16_t *target) {
 
 		// Maximum total output was 32 channels times a 16-bit range. Map that down.
 		// TODO: dynamic total volume?
-		target[sample] = (output * output_range_) >> 20;
+		Outputs::Speaker::apply<action>(
+			target[sample],
+			Outputs::Speaker::MonoSample(
+				(output * output_range_) >> 20
+			)
+		);
 
 		// Apply any RAM writes that interleave here.
 		++pending_store_read_time_;
diff --git a/Machines/Apple/AppleIIgs/Sound.hpp b/Machines/Apple/AppleIIgs/Sound.hpp
index c65e9ceb9..ea25afba7 100644
--- a/Machines/Apple/AppleIIgs/Sound.hpp
+++ b/Machines/Apple/AppleIIgs/Sound.hpp
@@ -34,9 +34,9 @@ class GLU: public Outputs::Speaker::BufferSource<GLU, false> {	// TODO: isn't th
 		bool get_interrupt_line();
 
 		// SampleSource.
-		void get_samples(std::size_t number_of_samples, std::int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
-		void skip_samples(const std::size_t number_of_samples);
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
@@ -94,7 +94,8 @@ class GLU: public Outputs::Speaker::BufferSource<GLU, false> {	// TODO: isn't th
 
 		// Functions to update an EnsoniqState; these don't belong to the state itself
 		// because they also access the pending stores (inter alia).
-		void generate_audio(size_t number_of_samples, std::int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void generate_audio(size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void skip_audio(EnsoniqState &state, size_t number_of_samples);
 
 		// Audio-thread state.
diff --git a/Machines/Apple/Macintosh/Audio.cpp b/Machines/Apple/Macintosh/Audio.cpp
index caa312248..2eab2a710 100644
--- a/Machines/Apple/Macintosh/Audio.cpp
+++ b/Machines/Apple/Macintosh/Audio.cpp
@@ -71,7 +71,8 @@ void Audio::set_volume_multiplier() {
 	volume_multiplier_ = int16_t(output_volume_ * volume_ * enabled_mask_);
 }
 
-void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
+template <Outputs::Speaker::Action action>
+void Audio::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	// TODO: the implementation below acts as if the hardware uses pulse-amplitude modulation;
 	// in fact it uses pulse-width modulation. But the scale for pulses isn't specified, so
 	// that's something to return to.
@@ -82,7 +83,7 @@ void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
 
 		// Determine the output level, and output that many samples.
 		const int16_t output_level = volume_multiplier_ * (int16_t(sample_queue_.buffer[sample_queue_.read_pointer].load(std::memory_order::memory_order_relaxed)) - 128);
-		std::fill(target, target + cycles_left_in_sample, output_level);
+		Outputs::Speaker::fill<action>(target, target + cycles_left_in_sample, output_level);
 		target += cycles_left_in_sample;
 
 		// Advance the sample pointer.
@@ -94,3 +95,6 @@ void Audio::get_samples(std::size_t number_of_samples, int16_t *target) {
 		number_of_samples -= cycles_left_in_sample;
 	}
 }
+template void Audio::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void Audio::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void Audio::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
diff --git a/Machines/Apple/Macintosh/Audio.hpp b/Machines/Apple/Macintosh/Audio.hpp
index 09781c5fa..1adb4b06a 100644
--- a/Machines/Apple/Macintosh/Audio.hpp
+++ b/Machines/Apple/Macintosh/Audio.hpp
@@ -50,7 +50,8 @@ class Audio: public ::Outputs::Speaker::BufferSource<Audio, false> {
 		void set_enabled(bool on);
 
 		// to satisfy ::Outputs::Speaker (included via ::Outputs::Filter.
-		void get_samples(std::size_t number_of_samples, int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		bool is_zero_level() const;
 		void set_sample_volume_range(std::int16_t range);
 
diff --git a/Machines/Atari/2600/TIASound.cpp b/Machines/Atari/2600/TIASound.cpp
index d109c3187..22ab1aec7 100644
--- a/Machines/Atari/2600/TIASound.cpp
+++ b/Machines/Atari/2600/TIASound.cpp
@@ -40,9 +40,10 @@ void Atari2600::TIASound::set_control(int channel, uint8_t control) {
 #define advance_poly5(c) poly5_counter_[channel] = (poly5_counter_[channel] >> 1) | (((poly5_counter_[channel] << 4) ^ (poly5_counter_[channel] << 2))&0x010)
 #define advance_poly9(c) poly9_counter_[channel] = (poly9_counter_[channel] >> 1) | (((poly9_counter_[channel] << 4) ^ (poly9_counter_[channel] << 8))&0x100)
 
-void Atari2600::TIASound::get_samples(std::size_t number_of_samples, int16_t *target) {
+template <Outputs::Speaker::Action action>
+void Atari2600::TIASound::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
 	for(unsigned int c = 0; c < number_of_samples; c++) {
-		target[c] = 0;
+		Outputs::Speaker::MonoSample output = 0;
 		for(int channel = 0; channel < 2; channel++) {
 			divider_counter_[channel] ++;
 			int divider_value = divider_counter_[channel] / (38 / CPUTicksPerAudioTick);
@@ -119,10 +120,14 @@ void Atari2600::TIASound::get_samples(std::size_t number_of_samples, int16_t *ta
 				break;
 			}
 
-			target[c] += (volume_[channel] * per_channel_volume_ * level) >> 4;
+			output += (volume_[channel] * per_channel_volume_ * level) >> 4;
 		}
+		Outputs::Speaker::apply<action>(target[c], output);
 	}
 }
+template void Atari2600::TIASound::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void Atari2600::TIASound::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void Atari2600::TIASound::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
 
 void Atari2600::TIASound::set_sample_volume_range(std::int16_t range) {
 	per_channel_volume_ = range / 2;
diff --git a/Machines/Atari/2600/TIASound.hpp b/Machines/Atari/2600/TIASound.hpp
index c1cace014..a71a16e9e 100644
--- a/Machines/Atari/2600/TIASound.hpp
+++ b/Machines/Atari/2600/TIASound.hpp
@@ -26,7 +26,8 @@ class TIASound: public Outputs::Speaker::BufferSource<TIASound, false> {
 		void set_control(int channel, uint8_t control);
 
 		// To satisfy ::SampleSource.
-		void get_samples(std::size_t number_of_samples, int16_t *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
 
 	private:
diff --git a/Machines/Electron/SoundGenerator.cpp b/Machines/Electron/SoundGenerator.cpp
index f0a58f5c5..14aa4fa22 100644
--- a/Machines/Electron/SoundGenerator.cpp
+++ b/Machines/Electron/SoundGenerator.cpp
@@ -19,21 +19,26 @@ void SoundGenerator::set_sample_volume_range(std::int16_t range) {
 	volume_ = unsigned(range / 2);
 }
 
-void SoundGenerator::get_samples(std::size_t number_of_samples, int16_t *target) {
+template <Outputs::Speaker::Action action>
+void SoundGenerator::apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target) {
+	if constexpr (action == Outputs::Speaker::Action::Ignore) {
+		counter_ = (counter_ + number_of_samples) % ((divider_+1) * 2);
+		return;
+	}
+
 	if(is_enabled_) {
 		while(number_of_samples--) {
-			*target = int16_t((counter_ / (divider_+1)) * volume_);
+			Outputs::Speaker::apply<action>(*target, Outputs::Speaker::MonoSample((counter_ / (divider_+1)) * volume_));
 			target++;
 			counter_ = (counter_ + 1) % ((divider_+1) * 2);
 		}
 	} else {
-		std::memset(target, 0, sizeof(int16_t) * number_of_samples);
+		Outputs::Speaker::fill<action>(target, target + number_of_samples, Outputs::Speaker::MonoSample(0));
 	}
 }
-
-void SoundGenerator::skip_samples(std::size_t number_of_samples) {
-	counter_ = (counter_ + number_of_samples) % ((divider_+1) * 2);
-}
+template void SoundGenerator::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::MonoSample *);
+template void SoundGenerator::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::MonoSample *);
+template void SoundGenerator::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::MonoSample *);
 
 void SoundGenerator::set_divider(uint8_t divider) {
 	audio_queue_.enqueue([this, divider]() {
diff --git a/Machines/Electron/SoundGenerator.hpp b/Machines/Electron/SoundGenerator.hpp
index 3222c68da..e787695ab 100644
--- a/Machines/Electron/SoundGenerator.hpp
+++ b/Machines/Electron/SoundGenerator.hpp
@@ -24,8 +24,8 @@ class SoundGenerator: public ::Outputs::Speaker::BufferSource<SoundGenerator, fa
 		static constexpr unsigned int clock_rate_divider = 8;
 
 		// To satisfy ::SampleSource.
-		void get_samples(std::size_t number_of_samples, int16_t *target);
-		void skip_samples(std::size_t number_of_samples);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
 
 	private:
diff --git a/Machines/Enterprise/Dave.cpp b/Machines/Enterprise/Dave.cpp
index ba079087b..5da74b673 100644
--- a/Machines/Enterprise/Dave.cpp
+++ b/Machines/Enterprise/Dave.cpp
@@ -99,7 +99,8 @@ void Audio::update_channel(int c) {
 	channels_[c].output |= output;
 }
 
-void Audio::get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target) {
+template <Outputs::Speaker::Action action>
+void Audio::apply_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target) {
 	Outputs::Speaker::StereoSample output_level;
 
 	size_t c = 0;
@@ -130,7 +131,7 @@ void Audio::get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoS
 
 		while(global_divider_ && c < number_of_samples) {
 			--global_divider_;
-			target[c] = output_level;
+			Outputs::Speaker::apply<action>(target[c], output_level);
 			++c;
 		}
 		global_divider_ = global_divider_reload_;
@@ -203,6 +204,9 @@ void Audio::get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoS
 		}
 	}
 }
+template void Audio::apply_samples<Outputs::Speaker::Action::Mix>(std::size_t, Outputs::Speaker::StereoSample *);
+template void Audio::apply_samples<Outputs::Speaker::Action::Store>(std::size_t, Outputs::Speaker::StereoSample *);
+template void Audio::apply_samples<Outputs::Speaker::Action::Ignore>(std::size_t, Outputs::Speaker::StereoSample *);
 
 // MARK: - Interrupt source
 
diff --git a/Machines/Enterprise/Dave.hpp b/Machines/Enterprise/Dave.hpp
index 8e5b70622..7951ae1a6 100644
--- a/Machines/Enterprise/Dave.hpp
+++ b/Machines/Enterprise/Dave.hpp
@@ -37,7 +37,8 @@ class Audio: public Outputs::Speaker::BufferSource<Audio, true> {
 
 		// MARK: - SampleSource.
 		void set_sample_volume_range(int16_t range);
-		void get_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::StereoSample *target);
 
 	private:
 		Concurrency::AsyncTaskQueue<false> &audio_queue_;
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme
index 19b54b90e..474fa352e 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/xcshareddata/xcschemes/Clock Signal.xcscheme	
@@ -62,7 +62,7 @@
       </Testables>
    </TestAction>
    <LaunchAction
-      buildConfiguration = "Release"
+      buildConfiguration = "Debug"
       selectedDebuggerIdentifier = "Xcode.DebuggerFoundation.Debugger.LLDB"
       selectedLauncherIdentifier = "Xcode.DebuggerFoundation.Launcher.LLDB"
       enableASanStackUseAfterReturn = "YES"
diff --git a/Outputs/Speaker/Implementation/BufferSource.hpp b/Outputs/Speaker/Implementation/BufferSource.hpp
index f493ea338..091f9f31e 100644
--- a/Outputs/Speaker/Implementation/BufferSource.hpp
+++ b/Outputs/Speaker/Implementation/BufferSource.hpp
@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include <algorithm>
 #include <array>
 #include <cstddef>
 #include <cstdint>
@@ -16,6 +17,38 @@
 
 namespace Outputs::Speaker {
 
+enum class Action {
+	/// New values should be _stored_ to the sample buffer.
+	Store,
+	/// New values should be _added_ to the sample buffer.
+	Mix,
+	/// New values shouldn't be stored; the source can skip generation of them if desired.
+	Ignore,
+};
+
+template <Action action, typename SampleT> void apply(SampleT &lhs, SampleT rhs) {
+	switch(action) {
+		case Action::Mix:	lhs += rhs;	break;
+		case Action::Store:	lhs = rhs;	break;
+		case Action::Ignore:			break;
+	}
+}
+
+template <Action action, typename IteratorT, typename SampleT> void fill(IteratorT begin, IteratorT end, SampleT value) {
+	switch(action) {
+		case Action::Mix:
+			while(begin != end) {
+				apply<action>(*begin, value);
+				++begin;
+			}
+		break;
+		case Action::Store:
+			std::fill(begin, end, value);
+		break;
+		case Action::Ignore:	break;
+	}
+}
+
 /*!
 	A sample source is something that can provide a stream of audio.
 	This optional base class provides the interface expected to be exposed
@@ -30,20 +63,11 @@ class BufferSource {
 		static constexpr bool is_stereo = stereo;
 
 		/*!
-			Should write the next @c number_of_samples to @c target.
+			Should 'apply' the next @c number_of_samples to @c target ; application means applying @c action which can be achieved either via the
+			helper functions above — @c apply and @c fill — or by semantic inspection (primarily, if an obvious quick route for @c Action::Ignore is available)
 		*/
-		void get_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] typename SampleT<stereo>::type *target) {}
-
-		/*!
-			Should skip the next @c number_of_samples. Subclasses of this SampleSource
-			need not implement this if it would no more efficient to do so than it is
-			merely to call get_samples and throw the result away, as per the default
-			implementation below.
-		*/
-		void skip_samples(std::size_t number_of_samples) {
-			typename SampleT<stereo>::type scratch_pad[number_of_samples];
-			get_samples(number_of_samples, scratch_pad);
-		}
+		template <Action action>
+		void apply_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] typename SampleT<stereo>::type *target) {}
 
 		/*!
 			@returns @c true if it is trivially true that a call to get_samples would just
@@ -75,13 +99,15 @@ class BufferSource {
 template <typename SourceT, bool stereo, int divider = 1>
 struct SampleSource: public BufferSource<SourceT, stereo> {
 	public:
-		void get_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target) {
+		template <bool mix>
+		void apply_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target) {
 			const auto &source = *static_cast<SourceT *>(this);
 
 			if constexpr (divider == 1) {
 				while(number_of_samples--) {
-					*target = source.level();
+					apply<mix>(*target, source.level());
 					++target;
+					source.advance();
 				}
 			} else {
 				std::size_t c = 0;
@@ -89,7 +115,7 @@ struct SampleSource: public BufferSource<SourceT, stereo> {
 				// Fill in the tail of any partially-captured level.
 				auto level = source.level();
 				while(c < number_of_samples && master_divider_ != divider) {
-					target[c] = level;
+					apply<mix>(target[c], level);
 					++c;
 					++master_divider_;
 				}
@@ -98,7 +124,7 @@ struct SampleSource: public BufferSource<SourceT, stereo> {
 				// Provide all full levels.
 				int whole_steps = (number_of_samples - c) / divider;
 				while(whole_steps--) {
-					std::fill(&target[c], &target[c + divider], source.level());
+					fill<mix>(&target[c], &target[c + divider], source.level());
 					c += divider;
 					source.advance();
 				}
@@ -106,31 +132,7 @@ struct SampleSource: public BufferSource<SourceT, stereo> {
 				// Provide the head of a further partial capture.
 				level = source.level();
 				master_divider_ = number_of_samples - c;
-				std::fill(&target[c], &target[number_of_samples], source.level());
-			}
-		}
-
-		void skip_samples(std::size_t number_of_samples) {
-			const auto &source = *static_cast<SourceT *>(this);
-
-			if constexpr (&SourceT::advance == &SampleSource::advance) {
-				return;
-			}
-
-			if constexpr (divider == 1) {
-				while(--number_of_samples) {
-					source.advance();
-				}
-			} else {
-				if(number_of_samples >= divider - master_divider_) {
-					source.advance();
-					number_of_samples -= (divider - master_divider_);
-				}
-				while(number_of_samples > divider) {
-					advance();
-					number_of_samples -= divider;
-				}
-				master_divider_ = number_of_samples;
+				fill<mix>(&target[c], &target[number_of_samples], source.level());
 			}
 		}
 
diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index cfdf3d962..f3fdff68c 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -49,14 +49,13 @@ template <typename... T> class CompoundSource:
 	private:
 		template <typename... S> class CompoundSourceHolder {
 			public:
-				template <bool output_stereo>
-				void get_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
+				template <Outputs::Speaker::Action action, bool output_stereo>
+				void apply_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
 					// Default-construct all samples, to fill with silence.
-					std::fill(target, target + number_of_samples, typename SampleT<output_stereo>::type());
+					Outputs::Speaker::fill<action>(target, target + number_of_samples, typename SampleT<output_stereo>::type());
 				}
 
 				void set_scaled_volume_range(int16_t, double *, double) {}
-				void skip_samples(const std::size_t) {}
 
 				static constexpr std::size_t size() {
 					return 0;
@@ -75,8 +74,8 @@ template <typename... T> class CompoundSource:
 
 				static constexpr bool is_stereo = S::is_stereo || CompoundSourceHolder<R...>::is_stereo;
 
-				template <bool output_stereo>
-				void get_samples(std::size_t number_of_samples, typename ::Outputs::Speaker::SampleT<output_stereo>::type *target) {
+				template <Outputs::Speaker::Action action, bool output_stereo>
+				void apply_samples(std::size_t number_of_samples, typename ::Outputs::Speaker::SampleT<output_stereo>::type *target) {
 
 					// If this is the step at which a mono-to-stereo adaptation happens, apply it.
 					if constexpr (output_stereo && !S::is_stereo) {
@@ -87,40 +86,26 @@ template <typename... T> class CompoundSource:
 						}
 
 						// Populate the conversion buffer with this source and all below.
-						get_samples<false>(number_of_samples, conversion_source_.data());
+						apply_samples<Action::Store, false>(number_of_samples, conversion_source_.data());
 
 						// Map up and return.
 						for(std::size_t c = 0; c < number_of_samples; c++) {
-							target[c].left = target[c].right = conversion_source_[c];
+							Outputs::Speaker::apply<action>(target[c].left, StereoSample(conversion_source_[c]));
 						}
 						return;
 					}
 
 					// Get the rest of the output.
-					next_source_.template get_samples<output_stereo>(number_of_samples, target);
+					next_source_.template apply_samples<action, output_stereo>(number_of_samples, target);
 
 					if(source_.is_zero_level()) {
 						// This component is currently outputting silence; therefore don't add anything to the output
 						// audio — just pass the call onward.
-						source_.skip_samples(number_of_samples);
 						return;
 					}
 
-					// Get this component's output.
-					typename SampleT<output_stereo>::type local_samples[number_of_samples];
-					source_.get_samples(number_of_samples, local_samples);
-
-					// Merge it in.
-					while(number_of_samples--) {
-						target[number_of_samples] += local_samples[number_of_samples];
-					}
-
-					// TODO: accelerate above?
-				}
-
-				void skip_samples(const std::size_t number_of_samples) {
-					source_.skip_samples(number_of_samples);
-					next_source_.skip_samples(number_of_samples);
+					// Add in this component's output.
+					source_.template apply_samples<Action::Mix>(number_of_samples, target);
 				}
 
 				void set_scaled_volume_range(int16_t range, double *volumes, double scale) {
@@ -157,12 +142,9 @@ template <typename... T> class CompoundSource:
 			}
 		}
 
-		void get_samples(std::size_t number_of_samples, Sample *target) {
-			source_holder_.template get_samples<::Outputs::Speaker::is_stereo<T...>()>(number_of_samples, target);
-		}
-
-		void skip_samples(const std::size_t number_of_samples) {
-			source_holder_.skip_samples(number_of_samples);
+		template <Outputs::Speaker::Action action>
+		void apply_samples(std::size_t number_of_samples, Sample *target) {
+			source_holder_.template apply_samples<action, ::Outputs::Speaker::is_stereo<T...>()>(number_of_samples, target);
 		}
 
 		/*!
diff --git a/Outputs/Speaker/Implementation/LowpassSpeaker.hpp b/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
index 5634de15d..4b3d5d16e 100644
--- a/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
+++ b/Outputs/Speaker/Implementation/LowpassSpeaker.hpp
@@ -8,6 +8,7 @@
 
 #pragma once
 
+#include "BufferSource.hpp"
 #include "../Speaker.hpp"
 #include "../../../SignalProcessing/FIRFilter.hpp"
 #include "../../../ClockReceiver/ClockReceiver.hpp"
@@ -396,7 +397,7 @@ template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpa
 		SampleSource &sample_source_;
 
 		void skip_samples(size_t count) {
-			sample_source_.skip_samples(count);
+			sample_source_.template apply_samples<Action::Ignore>(count, nullptr);
 		}
 
 		int get_scale() {
@@ -406,9 +407,9 @@ template <typename SampleSource> class PullLowpass: public LowpassBase<PullLowpa
 		void get_samples(size_t length, int16_t *target) {
 			if constexpr (SampleSource::is_stereo) {
 				StereoSample *const stereo_target = reinterpret_cast<StereoSample *>(target);
-				sample_source_.get_samples(length, stereo_target);
+				sample_source_.template apply_samples<Action::Store>(length, stereo_target);
 			} else {
-				sample_source_.get_samples(length, target);
+				sample_source_.template apply_samples<Action::Store>(length, target);
 			}
 		}
 };
diff --git a/Outputs/Speaker/Speaker.hpp b/Outputs/Speaker/Speaker.hpp
index 860395536..edeee7811 100644
--- a/Outputs/Speaker/Speaker.hpp
+++ b/Outputs/Speaker/Speaker.hpp
@@ -27,6 +27,9 @@ struct StereoSample {
 		left = rhs.left;
 		right = rhs.right;
 	}
+	StereoSample(MonoSample value) {
+		left = right = value;
+	}
 
 	StereoSample &operator +=(const StereoSample &rhs) {
 		left += rhs.left;

From 1895b4ee5d652e732f67a7b80284aeb82001c889 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Feb 2024 13:59:03 -0500
Subject: [PATCH 17/20] Remove empty implementation, the better for debugging.

---
 Machines/Electron/SoundGenerator.hpp            | 2 +-
 Outputs/Speaker/Implementation/BufferSource.hpp | 6 ++++--
 2 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/Machines/Electron/SoundGenerator.hpp b/Machines/Electron/SoundGenerator.hpp
index e787695ab..4699b9984 100644
--- a/Machines/Electron/SoundGenerator.hpp
+++ b/Machines/Electron/SoundGenerator.hpp
@@ -23,7 +23,7 @@ class SoundGenerator: public ::Outputs::Speaker::BufferSource<SoundGenerator, fa
 
 		static constexpr unsigned int clock_rate_divider = 8;
 
-		// To satisfy ::SampleSource.
+		// For BufferSource.
 		template <Outputs::Speaker::Action action>
 		void apply_samples(std::size_t number_of_samples, Outputs::Speaker::MonoSample *target);
 		void set_sample_volume_range(std::int16_t range);
diff --git a/Outputs/Speaker/Implementation/BufferSource.hpp b/Outputs/Speaker/Implementation/BufferSource.hpp
index 091f9f31e..da90dcba6 100644
--- a/Outputs/Speaker/Implementation/BufferSource.hpp
+++ b/Outputs/Speaker/Implementation/BufferSource.hpp
@@ -64,10 +64,12 @@ class BufferSource {
 
 		/*!
 			Should 'apply' the next @c number_of_samples to @c target ; application means applying @c action which can be achieved either via the
-			helper functions above — @c apply and @c fill — or by semantic inspection (primarily, if an obvious quick route for @c Action::Ignore is available)
+			helper functions above — @c apply and @c fill — or by semantic inspection (primarily, if an obvious quick route for @c Action::Ignore is available).
+
+			No default implementation is provided.
 		*/
 		template <Action action>
-		void apply_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] typename SampleT<stereo>::type *target) {}
+		void apply_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] typename SampleT<stereo>::type *target);
 
 		/*!
 			@returns @c true if it is trivially true that a call to get_samples would just

From 3d2d9ac45ed088c21089987beec5d941f93c7d79 Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Feb 2024 14:00:08 -0500
Subject: [PATCH 18/20] Remove default set_sample_volume_range implementation
 too.

---
 Outputs/Speaker/Implementation/BufferSource.hpp | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/Outputs/Speaker/Implementation/BufferSource.hpp b/Outputs/Speaker/Implementation/BufferSource.hpp
index da90dcba6..f5d4f7573 100644
--- a/Outputs/Speaker/Implementation/BufferSource.hpp
+++ b/Outputs/Speaker/Implementation/BufferSource.hpp
@@ -69,7 +69,7 @@ class BufferSource {
 			No default implementation is provided.
 		*/
 		template <Action action>
-		void apply_samples([[maybe_unused]] std::size_t number_of_samples, [[maybe_unused]] typename SampleT<stereo>::type *target);
+		void apply_samples(std::size_t number_of_samples, typename SampleT<stereo>::type *target);
 
 		/*!
 			@returns @c true if it is trivially true that a call to get_samples would just
@@ -82,7 +82,7 @@ class BufferSource {
 			Sets the proper output range for this sample source; it should write values
 			between 0 and volume.
 		*/
-		void set_sample_volume_range([[maybe_unused]] std::int16_t volume) {}
+		void set_sample_volume_range(std::int16_t volume);
 
 		/*!
 			Permits a sample source to declare that, averaged over time, it will use only

From f14e45f93ed89e6b8571f561574f23ddcd94d77a Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Feb 2024 14:23:54 -0500
Subject: [PATCH 19/20] Remove various instances of ';;'.

---
 Machines/Amiga/Amiga.cpp                                | 2 +-
 Machines/Apple/AppleIIgs/Sound.cpp                      | 2 +-
 Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp      | 2 +-
 OSBindings/SDL/main.cpp                                 | 2 +-
 Processors/65816/Implementation/65816Implementation.hpp | 2 +-
 Reflection/Struct.cpp                                   | 2 +-
 Storage/Disk/Encodings/MFM/Parser.cpp                   | 2 +-
 7 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/Machines/Amiga/Amiga.cpp b/Machines/Amiga/Amiga.cpp
index acce943d3..834ec0058 100644
--- a/Machines/Amiga/Amiga.cpp
+++ b/Machines/Amiga/Amiga.cpp
@@ -221,7 +221,7 @@ class ConcreteMachine:
 		// MARK: - MachineTypes::MouseMachine.
 
 		Inputs::Mouse &get_mouse() final {
-			return chipset_.get_mouse();;
+			return chipset_.get_mouse();
 		}
 
 		// MARK: - MachineTypes::JoystickMachine.
diff --git a/Machines/Apple/AppleIIgs/Sound.cpp b/Machines/Apple/AppleIIgs/Sound.cpp
index d52d6f3e3..84b0dda5c 100644
--- a/Machines/Apple/AppleIIgs/Sound.cpp
+++ b/Machines/Apple/AppleIIgs/Sound.cpp
@@ -108,7 +108,7 @@ uint8_t GLU::get_data() {
 
 	switch(address & 0xe0) {
 		case 0x00:	return local_.oscillators[address & 0x1f].velocity & 0xff;
-		case 0x20:	return local_.oscillators[address & 0x1f].velocity >> 8;;
+		case 0x20:	return local_.oscillators[address & 0x1f].velocity >> 8;
 		case 0x40:	return local_.oscillators[address & 0x1f].volume;
 		case 0x60:	return local_.oscillators[address & 0x1f].sample(local_.ram_);	// i.e. look up what the sample was on demand.
 		case 0x80:	return local_.oscillators[address & 0x1f].address;
diff --git a/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp b/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp
index 981f0b923..21a28066b 100644
--- a/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp
+++ b/Machines/Apple/Macintosh/DriveSpeedAccumulator.hpp
@@ -28,7 +28,7 @@ class DriveSpeedAccumulator {
 			Sets the delegate to receive drive speed changes.
 		*/
 		void set_delegate(Delegate *delegate) {
-			delegate_ = delegate;;
+			delegate_ = delegate;
 		}
 
 	private:
diff --git a/OSBindings/SDL/main.cpp b/OSBindings/SDL/main.cpp
index 1da6e2c8f..17657e81c 100644
--- a/OSBindings/SDL/main.cpp
+++ b/OSBindings/SDL/main.cpp
@@ -562,7 +562,7 @@ int main(int argc, char *argv[]) {
 		}
 		std::cout << "." << std::endl << std::endl;
 
-		std::cout << "Further machine options:" << std::endl << std::endl;;
+		std::cout << "Further machine options:" << std::endl << std::endl;
 
 		const auto targets = Machine::TargetsByMachineName(false);
 		const auto runtime_options = Machine::AllOptionsByMachineName();
diff --git a/Processors/65816/Implementation/65816Implementation.hpp b/Processors/65816/Implementation/65816Implementation.hpp
index be8492f77..6dd58d050 100644
--- a/Processors/65816/Implementation/65816Implementation.hpp
+++ b/Processors/65816/Implementation/65816Implementation.hpp
@@ -793,7 +793,7 @@ template <typename BusHandler, bool uses_ready_line> void Processor<BusHandler,
 							assert(data_buffer_.size == 2 - m_flag());
 							++data_buffer_.value;
 							registers_.flags.set_nz(uint16_t(data_buffer_.value), registers_.m_shift);
-						break;;
+						break;
 
 						case DEC:
 							assert(data_buffer_.size == 2 - m_flag());
diff --git a/Reflection/Struct.cpp b/Reflection/Struct.cpp
index babd12744..81c62fb2e 100644
--- a/Reflection/Struct.cpp
+++ b/Reflection/Struct.cpp
@@ -110,7 +110,7 @@ template <> bool Reflection::set(Struct &target, const std::string &name, bool v
 	if(!target_type) return false;
 
 	if(*target_type == typeid(bool)) {
-		target.set(name, &value, offset);;
+		target.set(name, &value, offset);
 	}
 
 	return false;
diff --git a/Storage/Disk/Encodings/MFM/Parser.cpp b/Storage/Disk/Encodings/MFM/Parser.cpp
index 7f3a848e7..b6ad3a58a 100644
--- a/Storage/Disk/Encodings/MFM/Parser.cpp
+++ b/Storage/Disk/Encodings/MFM/Parser.cpp
@@ -37,7 +37,7 @@ void Parser::install_track(const Storage::Disk::Track::Address &address) {
 		// Just try all three in succession.
 		append(parse_track(*track, Density::Single), sectors_by_id);
 		append(parse_track(*track, Density::Double), sectors_by_id);
-		append(parse_track(*track, Density::High), sectors_by_id);;
+		append(parse_track(*track, Density::High), sectors_by_id);
 	}
 
 	sectors_by_address_by_track_.emplace(address, std::move(sectors_by_id));

From 507c3da927957cb847ca01a3cec1a346ce0bcc0c Mon Sep 17 00:00:00 2001
From: Thomas Harte <thomas.harte@gmail.com>
Date: Mon, 12 Feb 2024 14:33:55 -0500
Subject: [PATCH 20/20] Sometimes avoid unnecessary zero-fills.

---
 .../Speaker/Implementation/CompoundSource.hpp | 34 ++++++++-----------
 1 file changed, 14 insertions(+), 20 deletions(-)

diff --git a/Outputs/Speaker/Implementation/CompoundSource.hpp b/Outputs/Speaker/Implementation/CompoundSource.hpp
index f3fdff68c..bdfe93545 100644
--- a/Outputs/Speaker/Implementation/CompoundSource.hpp
+++ b/Outputs/Speaker/Implementation/CompoundSource.hpp
@@ -49,23 +49,10 @@ template <typename... T> class CompoundSource:
 	private:
 		template <typename... S> class CompoundSourceHolder {
 			public:
-				template <Outputs::Speaker::Action action, bool output_stereo>
-				void apply_samples(std::size_t number_of_samples, typename SampleT<output_stereo>::type *target) {
-					// Default-construct all samples, to fill with silence.
-					Outputs::Speaker::fill<action>(target, target + number_of_samples, typename SampleT<output_stereo>::type());
-				}
-
-				void set_scaled_volume_range(int16_t, double *, double) {}
-
-				static constexpr std::size_t size() {
-					return 0;
-				}
-
 				static constexpr bool is_stereo = false;
-
-				double total_scale(double *) const {
-					return 0.0;
-				}
+				void set_scaled_volume_range(int16_t, double *, double) {}
+				static constexpr std::size_t size() {	return 0;	}
+				double total_scale(double *) const {	return 0.0;	}
 		};
 
 		template <typename S, typename... R> class CompoundSourceHolder<S, R...> {
@@ -95,17 +82,24 @@ template <typename... T> class CompoundSource:
 						return;
 					}
 
-					// Get the rest of the output.
-					next_source_.template apply_samples<action, output_stereo>(number_of_samples, target);
+					constexpr bool is_final_source = sizeof...(R) == 0;
+
+					// Get the rest of the output, if any.
+					if constexpr (!is_final_source) {
+						next_source_.template apply_samples<action, output_stereo>(number_of_samples, target);
+					}
 
 					if(source_.is_zero_level()) {
 						// This component is currently outputting silence; therefore don't add anything to the output
-						// audio — just pass the call onward.
+						// audio. Zero fill only if this is the final source (as everything above will be additive).
+						if constexpr (is_final_source) {
+							Outputs::Speaker::fill<action>(target, target + number_of_samples, typename SampleT<output_stereo>::type());
+						}
 						return;
 					}
 
 					// Add in this component's output.
-					source_.template apply_samples<Action::Mix>(number_of_samples, target);
+					source_.template apply_samples<is_final_source ? Action::Store : Action::Mix>(number_of_samples, target);
 				}
 
 				void set_scaled_volume_range(int16_t range, double *volumes, double scale) {