diff --git a/src/xenia/apu/audio_system.cc b/src/xenia/apu/audio_system.cc
index aa9eb8dac..0f34c4dd0 100644
--- a/src/xenia/apu/audio_system.cc
+++ b/src/xenia/apu/audio_system.cc
@@ -22,7 +22,8 @@ using namespace xe::cpu;
 
 AudioSystem::AudioSystem(Emulator* emulator) :
     emulator_(emulator), memory_(emulator->memory()),
-    thread_(0), running_(false), driver_(0) {
+    thread_(0), running_(false), driver_(0),
+    client_({ 0 }) {
   // Create the run loop used for any windows/etc.
   // This must be done on the thread we create the driver.
   run_loop_ = xe_run_loop_create();
@@ -86,16 +87,16 @@ void AudioSystem::ThreadStart() {
     }
 
     // Pump worker.
-    // mehhh
     xe_mutex_lock(lock_);
-    auto clients = clients_;
+    uint32_t client_callback = client_.callback;
+    uint32_t client_callback_arg = client_.wrapped_callback_arg;
     xe_mutex_unlock(lock_);
-    for (auto it = clients.begin(); it != clients.end(); ++it) {
+    if (client_callback) {
       processor->Execute(
-          thread_state_, it->callback, it->wrapped_callback_arg, 0);
+        thread_state_, client_callback, client_callback_arg, 0);
+    } else {
+      Sleep(500);
     }
-    //worker_->Pump();
-    Sleep(1000);
 
     if (!running_) {
       break;
@@ -127,11 +128,21 @@ void AudioSystem::Shutdown() {
 
 void AudioSystem::RegisterClient(
     uint32_t callback, uint32_t callback_arg) {
+  // Only support one client for now.
+  XEASSERTZERO(client_.callback);
+
   uint32_t ptr = (uint32_t)memory()->HeapAlloc(0, 0x4, 0);
   auto mem = memory()->membase();
   XESETUINT32BE(mem + ptr, callback_arg);
+
   xe_mutex_lock(lock_);
-  clients_.push_back({ callback, callback_arg, ptr });
+  client_ = { callback, callback_arg, ptr };
+  xe_mutex_unlock(lock_);
+}
+
+void AudioSystem::UnregisterClient() {
+  xe_mutex_lock(lock_);
+  client_ = { 0 };
   xe_mutex_unlock(lock_);
 }
 
diff --git a/src/xenia/apu/audio_system.h b/src/xenia/apu/audio_system.h
index c4e87f046..e8d3907b1 100644
--- a/src/xenia/apu/audio_system.h
+++ b/src/xenia/apu/audio_system.h
@@ -37,7 +37,8 @@ public:
   virtual void Shutdown();
 
   void RegisterClient(uint32_t callback, uint32_t callback_arg);
-  //void UnregisterClient();
+  void UnregisterClient();
+  virtual void SubmitFrame(uint32_t samples_ptr) = 0;
 
   bool HandlesRegister(uint64_t addr);
   virtual uint64_t ReadRegister(uint64_t addr);
@@ -76,14 +77,13 @@ protected:
   cpu::XenonThreadState* thread_state_;
   uint32_t          thread_block_;
   bool              running_;
-  xe_mutex_t*       lock_;
 
-  typedef struct {
+  xe_mutex_t*       lock_;
+  struct {
     uint32_t callback;
     uint32_t callback_arg;
     uint32_t wrapped_callback_arg;
-  } RenderDriverClient;
-  std::vector<RenderDriverClient> clients_;
+  } client_;
 
   AudioDriver*      driver_;
 };
diff --git a/src/xenia/apu/nop/nop_audio_system.cc b/src/xenia/apu/nop/nop_audio_system.cc
index 3354229af..f4d0caaa6 100644
--- a/src/xenia/apu/nop/nop_audio_system.cc
+++ b/src/xenia/apu/nop/nop_audio_system.cc
@@ -36,6 +36,10 @@ void NopAudioSystem::Pump() {
   //
 }
 
+void NopAudioSystem::SubmitFrame(uint32_t samples_ptr) {
+  // Process samples! They are big-endian floats.
+}
+
 void NopAudioSystem::Shutdown() {
   AudioSystem::Shutdown();
 }
diff --git a/src/xenia/apu/nop/nop_audio_system.h b/src/xenia/apu/nop/nop_audio_system.h
index ca82975bd..5a71aaf7d 100644
--- a/src/xenia/apu/nop/nop_audio_system.h
+++ b/src/xenia/apu/nop/nop_audio_system.h
@@ -28,6 +28,8 @@ public:
 
   virtual void Shutdown();
 
+  virtual void SubmitFrame(uint32_t samples_ptr);
+
 protected:
   virtual void Initialize();
   virtual void Pump();
diff --git a/src/xenia/kernel/xboxkrnl_audio.cc b/src/xenia/kernel/xboxkrnl_audio.cc
index 68f47a6b2..6ea55ea6f 100644
--- a/src/xenia/kernel/xboxkrnl_audio.cc
+++ b/src/xenia/kernel/xboxkrnl_audio.cc
@@ -111,8 +111,10 @@ SHIM_CALL XAudioUnregisterRenderDriverClient_shim(
       "XAudioUnregisterRenderDriverClient(%.8X)",
       driver_ptr);
 
+  XEASSERT(driver_ptr == 0xAADD1100);
+
   auto audio_system = state->emulator()->audio_system();
-  //audio_system->UnregisterClient(...);
+  audio_system->UnregisterClient();
 
   SHIM_SET_RETURN(X_ERROR_SUCCESS);
 }
@@ -127,8 +129,10 @@ SHIM_CALL XAudioSubmitRenderDriverFrame_shim(
       "XAudioSubmitRenderDriverFrame(%.8X, %.8X)",
       driver_ptr, samples_ptr);
 
+  XEASSERT(driver_ptr == 0xAADD1100);
+
   auto audio_system = state->emulator()->audio_system();
-  //audio_system->SubmitFrame();
+  audio_system->SubmitFrame(samples_ptr);
 
   SHIM_SET_RETURN(X_ERROR_SUCCESS);
 }