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