diff --git a/Machines/Apple/Macintosh/DeferredAudio.hpp b/Machines/Apple/Macintosh/DeferredAudio.hpp
new file mode 100644
index 000000000..72ebc6b10
--- /dev/null
+++ b/Machines/Apple/Macintosh/DeferredAudio.hpp
@@ -0,0 +1,34 @@
+//
+//  DeferredAudio.hpp
+//  Clock Signal
+//
+//  Created by Thomas Harte on 01/06/2019.
+//  Copyright © 2019 Thomas Harte. All rights reserved.
+//
+
+#ifndef DeferredAudio_h
+#define DeferredAudio_h
+
+#include "Audio.hpp"
+#include "../../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
+
+namespace Apple {
+namespace Macintosh {
+
+struct DeferredAudio {
+	Concurrency::DeferringAsyncTaskQueue queue;
+	Audio audio;
+	Outputs::Speaker::LowpassSpeaker<Audio> speaker;
+	HalfCycles time_since_update;
+
+	DeferredAudio() : audio(queue), speaker(audio) {}
+
+	void flush() {
+		speaker.run_for(queue, time_since_update.flush_cycles());
+	}
+};
+
+}
+}
+
+#endif /* DeferredAudio_h */
diff --git a/Machines/Apple/Macintosh/Macintosh.cpp b/Machines/Apple/Macintosh/Macintosh.cpp
index a03c10489..6d1946211 100644
--- a/Machines/Apple/Macintosh/Macintosh.cpp
+++ b/Machines/Apple/Macintosh/Macintosh.cpp
@@ -10,7 +10,7 @@
 
 #include <array>
 
-#include "Audio.hpp"
+#include "DeferredAudio.hpp"
 #include "Keyboard.hpp"
 #include "RealTimeClock.hpp"
 #include "Video.hpp"
@@ -21,7 +21,6 @@
 
 #include "../../../Components/6522/6522.hpp"
 #include "../../../Components/DiskII/IWM.hpp"
-#include "../../../Outputs/Speaker/Implementation/LowpassSpeaker.hpp"
 #include "../../../Processors/68000/68000.hpp"
 
 #include "../../Utility/MemoryPacker.hpp"
@@ -42,7 +41,7 @@ class ConcreteMachine:
 	public:
 		ConcreteMachine(const ROMMachine::ROMFetcher &rom_fetcher) :
 		 	mc68000_(*this),
-		 	video_(ram_.data()),
+		 	video_(ram_.data(), audio_),
 		 	via_(via_port_handler_),
 		 	via_port_handler_(*this, clock_, keyboard_, video_, audio_, iwm_),
 		 	iwm_(CLOCK_RATE) {
@@ -57,6 +56,7 @@ class ConcreteMachine:
 
 			// The Mac runs at 7.8336mHz.
 			set_clock_rate(double(CLOCK_RATE));
+			audio_.speaker.set_input_rate(float(CLOCK_RATE));
 		}
 
 		void set_scan_target(Outputs::Display::ScanTarget *scan_target) override {
@@ -243,8 +243,8 @@ class ConcreteMachine:
 			ROM_is_overlay_ = rom_is_overlay;
 		}
 
-		void set_use_alternate_screen_buffer(bool use_alternate_screen_buffer) {
-			video_.set_use_alternate_screen_buffer(use_alternate_screen_buffer);
+		void set_use_alternate_buffers(bool use_alternate_screen_buffer, bool use_alternate_audio_buffer) {
+			video_.set_use_alternate_buffers(use_alternate_screen_buffer, use_alternate_audio_buffer);
 		}
 
 	private:
@@ -259,22 +259,9 @@ class ConcreteMachine:
 			}
 		};
 
-		struct Audio {
-			Concurrency::DeferringAsyncTaskQueue queue;
-			Apple::Macintosh::Audio audio;
-			Outputs::Speaker::LowpassSpeaker<Apple::Macintosh::Audio> speaker;
-			HalfCycles time_since_update;
-
-			Audio() : audio(queue), speaker(audio) {}
-
-			void flush() {
-				speaker.run_for(queue, time_since_update.flush_cycles());
-			}
-		};
-
 		class VIAPortHandler: public MOS::MOS6522::PortHandler {
 			public:
-				VIAPortHandler(ConcreteMachine &machine, RealTimeClock &clock, Keyboard &keyboard, Video &video, Audio &audio, IWM &iwm) :
+				VIAPortHandler(ConcreteMachine &machine, RealTimeClock &clock, Keyboard &keyboard, Video &video, DeferredAudio &audio, IWM &iwm) :
 					machine_(machine), clock_(clock), keyboard_(keyboard), video_(video), audio_(audio), iwm_(iwm) {}
 
 				using Port = MOS::MOS6522::Port;
@@ -299,13 +286,11 @@ class ConcreteMachine:
 							iwm_.flush();
 							iwm_.iwm.set_select(!(value & 0x20));
 
-							machine_.set_use_alternate_screen_buffer(!(value & 0x40));
+							machine_.set_use_alternate_buffers(!(value & 0x40), !(value&0x08));
 							machine_.set_rom_is_overlay(!!(value & 0x10));
 
 							audio_.flush();
 							audio_.audio.set_volume(value & 7);
-
-							// TODO: alternate sound buffer.
 						break;
 
 						case Port::B:
@@ -360,7 +345,7 @@ class ConcreteMachine:
 				RealTimeClock &clock_;
 				Keyboard &keyboard_;
 				Video &video_;
-				Audio &audio_;
+				DeferredAudio &audio_;
 				IWM &iwm_;
 		};
 
@@ -369,8 +354,8 @@ class ConcreteMachine:
 
 		CPU::MC68000::Processor<ConcreteMachine, true> mc68000_;
 
+		DeferredAudio audio_;
 		Video video_;
-		Audio audio_;
 
 		RealTimeClock clock_;
 		Keyboard keyboard_;
diff --git a/Machines/Apple/Macintosh/Video.cpp b/Machines/Apple/Macintosh/Video.cpp
index 1028003a9..bcdf4b17f 100644
--- a/Machines/Apple/Macintosh/Video.cpp
+++ b/Machines/Apple/Macintosh/Video.cpp
@@ -33,7 +33,8 @@ const int sync_end = 38;
 //	"The visible portion of a full-screen display consists of 342 horizontal scan lines...
 //	During the vertical blanking interval, the turned-off beam ... traces out an additional 28 scan lines,"
 //
-Video::Video(uint16_t *ram) :
+Video::Video(uint16_t *ram, DeferredAudio &audio) :
+	audio_(audio),
  	crt_(704, 1, 370, Outputs::Display::ColourSpace::YIQ, 1, 1, 6, false, Outputs::Display::InputDataType::Luminance1),
  	ram_(ram) {
 
@@ -131,6 +132,14 @@ void Video::run_for(HalfCycles duration) {
 					crt_.output_blank((44 - sync_end) * 16);
 				}
 			}
+
+			// Audio and disk fetches occur "just before video data".
+			if(final_word == 44) {
+				const uint16_t audio_word = ram_[audio_address_];
+				++audio_address_;
+				audio_.audio.post_sample(audio_word >> 8);
+				// TODO: post disk byte.
+			}
 		}
 
 		duration -= cycles_left_in_line;
@@ -141,6 +150,12 @@ void Video::run_for(HalfCycles duration) {
 				Video: $1A700 and the alternate buffer starts at $12700; for a 512K Macintosh, add $60000 to these numbers.
 			*/
 			video_address_ = use_alternate_screen_buffer_ ? (0x12700 >> 1) : (0x1a700 >> 1);
+
+			/*
+				"The main sound buffer is at $1FD00 in a 128K Macintosh, and the alternate buffer is at $1A100;
+				for a 512K Macintosh, add $60000 to these values."
+			*/
+			audio_address_ = use_alternate_audio_buffer_ ? (0x1fd00 >> 1) : (0x1a100 >> 1);
 		}
 	}
 }
@@ -156,7 +171,7 @@ bool Video::is_outputting() {
 	return line < 342 && column < 32;
 }
 
-void Video::set_use_alternate_screen_buffer(bool use_alternate_screen_buffer) {
+void Video::set_use_alternate_buffers(bool use_alternate_screen_buffer, bool use_alternate_audio_buffer) {
 	use_alternate_screen_buffer_ = use_alternate_screen_buffer;
+	use_alternate_audio_buffer_ = use_alternate_audio_buffer;
 }
-
diff --git a/Machines/Apple/Macintosh/Video.hpp b/Machines/Apple/Macintosh/Video.hpp
index 041ffba13..612b0b92e 100644
--- a/Machines/Apple/Macintosh/Video.hpp
+++ b/Machines/Apple/Macintosh/Video.hpp
@@ -11,29 +11,38 @@
 
 #include "../../../Outputs/CRT/CRT.hpp"
 #include "../../../ClockReceiver/ClockReceiver.hpp"
+#include "DeferredAudio.hpp"
 
 namespace Apple {
 namespace Macintosh {
 
 class Video {
 	public:
-		Video(uint16_t *ram);
+		Video(uint16_t *ram, DeferredAudio &audio);
 		void set_scan_target(Outputs::Display::ScanTarget *scan_target);
 		void run_for(HalfCycles duration);
-		void set_use_alternate_screen_buffer(bool use_alternate_screen_buffer);
+
+		void set_use_alternate_buffers(bool use_alternate_screen_buffer, bool use_alternate_audio_buffer);
 
 		// TODO: feedback on blanks and syncs.
 		bool vsync();
 		bool is_outputting();
 
 	private:
+		DeferredAudio &audio_;
+		uint16_t *ram_ = nullptr;
+
 		Outputs::CRT::CRT crt_;
 
 		HalfCycles frame_position_;
+
 		size_t video_address_ = 0;
-		uint16_t *ram_ = nullptr;
+		size_t audio_address_ = 0;
+
 		uint8_t *pixel_buffer_ = nullptr;
+
 		bool use_alternate_screen_buffer_ = false;
+		bool use_alternate_audio_buffer_ = false;
 };
 
 }
diff --git a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj
index 10022b850..55d44c5bb 100644
--- a/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
+++ b/OSBindings/Mac/Clock Signal.xcodeproj/project.pbxproj	
@@ -1328,6 +1328,7 @@
 		4BB298EC1B587D8400A49093 /* txsn */ = {isa = PBXFileReference; lastKnownFileType = file; path = txsn; sourceTree = "<group>"; };
 		4BB298ED1B587D8400A49093 /* tyan */ = {isa = PBXFileReference; lastKnownFileType = file; path = tyan; sourceTree = "<group>"; };
 		4BB2A9AE1E13367E001A5C23 /* CRCTests.mm */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.objcpp; path = CRCTests.mm; sourceTree = "<group>"; };
+		4BB4BFAA22A300710069048D /* DeferredAudio.hpp */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.cpp.h; path = DeferredAudio.hpp; sourceTree = "<group>"; };
 		4BB697C61D4B558F00248BDF /* Factors.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; name = Factors.hpp; path = ../../NumberTheory/Factors.hpp; sourceTree = "<group>"; };
 		4BB697C91D4B6D3E00248BDF /* TimedEventLoop.cpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.cpp; path = TimedEventLoop.cpp; sourceTree = "<group>"; };
 		4BB697CA1D4B6D3E00248BDF /* TimedEventLoop.hpp */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.cpp.h; path = TimedEventLoop.hpp; sourceTree = "<group>"; };
@@ -3072,6 +3073,7 @@
 				4BCE0058227CFFCA000CA200 /* Macintosh.cpp */,
 				4BCE005E227D39AB000CA200 /* Video.cpp */,
 				4B9378E322A199C600973513 /* Audio.hpp */,
+				4BB4BFAA22A300710069048D /* DeferredAudio.hpp */,
 				4BDB3D8522833321002D3CEE /* Keyboard.hpp */,
 				4BCE0059227CFFCA000CA200 /* Macintosh.hpp */,
 				4BD0692B22828A2D00D2A54F /* RealTimeClock.hpp */,