diff --git a/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.cpp b/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.cpp
index 754a1f2..fc5df4c 100644
--- a/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.cpp
+++ b/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.cpp
@@ -80,6 +80,15 @@ void GpAudioChannelXAudio2::PostBuffer(const void *buffer, size_t bufferSize)
 	}
 }
 
+void GpAudioChannelXAudio2::Stop()
+{
+	// Set voice state BEFORE calling FlushSourceBuffers so state is idle before any callbacks trigger
+	m_sourceVoice->Stop(0, 0);
+	m_voiceState = VoiceState_Idle;
+
+	m_sourceVoice->FlushSourceBuffers();
+}
+
 void GpAudioChannelXAudio2::Destroy()
 {
 	this->~GpAudioChannelXAudio2();
diff --git a/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.h b/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.h
index cfcfb4c..b9317b2 100644
--- a/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.h
+++ b/GpAudioDriver_XAudio2/GpAudioChannelXAudio2.h
@@ -15,8 +15,9 @@ public:
 
 	static GpAudioChannelXAudio2 *Create(GpAudioDriverXAudio2 *driver);
 
-	void SetAudioChannelContext(IGpAudioChannelCallbacks *callbacks);
-	void PostBuffer(const void *buffer, size_t bufferSize);
+	void SetAudioChannelContext(IGpAudioChannelCallbacks *callbacks) override;
+	void PostBuffer(const void *buffer, size_t bufferSize) override;
+	void Stop() override;
 	void Destroy() override;
 
 	bool Init();
diff --git a/GpCommon/IGpAudioChannel.h b/GpCommon/IGpAudioChannel.h
index ab1dddd..3d34a26 100644
--- a/GpCommon/IGpAudioChannel.h
+++ b/GpCommon/IGpAudioChannel.h
@@ -6,5 +6,6 @@ struct IGpAudioChannel
 {
 	virtual void SetAudioChannelContext(IGpAudioChannelCallbacks *callbacks) = 0;
 	virtual void PostBuffer(const void *buffer, size_t bufferSize) = 0;
+	virtual void Stop() = 0;
 	virtual void Destroy() = 0;
 };
diff --git a/GpD3D/GpPLGlueAudioChannel.cpp b/GpD3D/GpPLGlueAudioChannel.cpp
index 1926e9c..5fb281d 100644
--- a/GpD3D/GpPLGlueAudioChannel.cpp
+++ b/GpD3D/GpPLGlueAudioChannel.cpp
@@ -16,6 +16,11 @@ void GpPLGlueAudioChannel::PostBuffer(const void *buffer, size_t bufferSize)
 	m_audioChannel->PostBuffer(buffer, bufferSize);
 }
 
+void GpPLGlueAudioChannel::Stop()
+{
+	m_audioChannel->Stop();
+}
+
 void GpPLGlueAudioChannel::Destroy()
 {
 	this->~GpPLGlueAudioChannel();
diff --git a/GpD3D/GpPLGlueAudioChannel.h b/GpD3D/GpPLGlueAudioChannel.h
index c0cbba4..a4780ed 100644
--- a/GpD3D/GpPLGlueAudioChannel.h
+++ b/GpD3D/GpPLGlueAudioChannel.h
@@ -10,6 +10,7 @@ class GpPLGlueAudioChannel final : public PortabilityLayer::HostAudioChannel, pu
 public:
 	void SetClientAudioChannelContext(PortabilityLayer::ClientAudioChannelContext *context) override;
 	void PostBuffer(const void *buffer, size_t bufferSize) override;
+	void Stop() override;
 	void Destroy() override;
 
 	void NotifyBufferFinished() override;
diff --git a/PortabilityLayer/HostAudioChannel.h b/PortabilityLayer/HostAudioChannel.h
index 303263e..4dbfb4d 100644
--- a/PortabilityLayer/HostAudioChannel.h
+++ b/PortabilityLayer/HostAudioChannel.h
@@ -9,6 +9,7 @@ namespace PortabilityLayer
 	public:
 		virtual void SetClientAudioChannelContext(ClientAudioChannelContext *context) = 0;
 		virtual void PostBuffer(const void *buffer, size_t bufferSize) = 0;
+		virtual void Stop() = 0;
 		virtual void Destroy() = 0;
 	};
 }
diff --git a/PortabilityLayer/PLSound.cpp b/PortabilityLayer/PLSound.cpp
index 037c02d..3d2ecab 100644
--- a/PortabilityLayer/PLSound.cpp
+++ b/PortabilityLayer/PLSound.cpp
@@ -19,6 +19,8 @@ namespace PortabilityLayer
 		~AudioChannelImpl();
 
 		bool PushCommand(const SndCommand &command, bool blocking);
+		void ClearAllCommands();
+		void Stop();
 
 		void NotifyBufferFinished() override;
 
@@ -196,6 +198,38 @@ namespace PortabilityLayer
 
 		return true;
 	}
+
+	void AudioChannelImpl::ClearAllCommands()
+	{
+		m_mutex->Lock();
+		m_numQueuedCommands = 0;
+		m_nextDequeueCommandPos = 0;
+		m_nextInsertCommandPos = 0;
+		m_mutex->Unlock();
+	}
+
+	void AudioChannelImpl::Stop()
+	{
+		m_mutex->Lock();
+		if (m_state == State_Idle)
+		{
+			m_mutex->Unlock();
+		}
+		else if (m_state == State_PlayingAsync)
+		{
+			m_state = State_FlushStarting;
+			m_audioChannel->Stop();
+			m_mutex->Unlock();
+
+			m_threadEvent->Wait();
+		}
+		else
+		{
+			m_mutex->Unlock();
+			assert(false);
+		}
+	}
+
 }
 
 OSErr GetDefaultOutputVolume(long *vol)
@@ -297,7 +331,17 @@ OSErr SndDoCommand(SndChannelPtr channel, const SndCommand *command, Boolean fai
 
 OSErr SndDoImmediate(SndChannelPtr channel, const SndCommand *command)
 {
-	PL_NotYetImplemented();
+	PortabilityLayer::AudioChannelImpl *audioChannelImpl = static_cast<PortabilityLayer::AudioChannelImpl*>(channel);
+
+	if (command->cmd == flushCmd)
+		audioChannelImpl->ClearAllCommands();
+	else if (command->cmd == quietCmd)
+		audioChannelImpl->Stop();
+	else
+	{
+		assert(false);
+		return genericErr;
+	}
+
 	return noErr;
 }
-