diff --git a/test/test_browser.py b/test/test_browser.py
index 36f27b55b6534..c1ce997417fee 100644
--- a/test/test_browser.py
+++ b/test/test_browser.py
@@ -5495,17 +5495,21 @@ def test_audio_worklet_post_function(self, args):
   def test_audio_worklet_modularize(self, args):
     self.btest_exit('webaudio/audioworklet.c', args=['-sAUDIO_WORKLET', '-sWASM_WORKERS', '-sMODULARIZE=1', '-sEXPORT_NAME=MyModule', '--shell-file', test_file('shell_that_launches_modularize.html')] + args)
 
-  # Tests multiple inputs, forcing a larger stack (note: passing BROWSER_TEST is
-  # specific to this test to allow it to exit rather than play forever).
+  # Tests an AudioWorklet with multiple stereo inputs mixing in the processor
+  # via a varying parameter to a single stereo output (touching all of the API
+  # copying from structs)
   @parameterized({
     '': ([],),
     'minimal_with_closure': (['-sMINIMAL_RUNTIME', '--closure=1', '-Oz'],),
   })
-  def test_audio_worklet_stereo_io(self, args):
+  @no_wasm64('https://github.com/emscripten-core/emscripten/pull/23508')
+  @no_2gb('https://github.com/emscripten-core/emscripten/pull/23508')
+  @requires_sound_hardware
+  def test_audio_worklet_params_mixing(self, args):
     os.mkdir('audio_files')
     shutil.copy(test_file('webaudio/audio_files/emscripten-beat.mp3'), 'audio_files/')
     shutil.copy(test_file('webaudio/audio_files/emscripten-bass.mp3'), 'audio_files/')
-    self.btest_exit('webaudio/audioworklet_in_out_stereo.c', args=['-sAUDIO_WORKLET', '-sWASM_WORKERS', '-DBROWSER_TEST'] + args)
+    self.btest_exit('webaudio/audioworklet_params_mixing.c', args=['-sAUDIO_WORKLET', '-sWASM_WORKERS', '-DTEST_AND_EXIT'] + args)
 
   def test_error_reporting(self):
     # Test catching/reporting Error objects
diff --git a/test/test_interactive.py b/test/test_interactive.py
index 78de7771cd5f7..e25bd12f4f9b2 100644
--- a/test/test_interactive.py
+++ b/test/test_interactive.py
@@ -334,10 +334,32 @@ def test_audio_worklet_2x_hard_pan_io(self):
     shutil.copy(test_file('webaudio/audio_files/emscripten-bass-mono.mp3'), 'audio_files/')
     self.btest_exit('webaudio/audioworklet_2x_in_hard_pan.c', args=['-sAUDIO_WORKLET', '-sWASM_WORKERS'])
 
+  # Tests an AudioWorklet with multiple stereo inputs mixing in the processor via a parameter to a single stereo output (6kB stack)
+  def test_audio_worklet_params_mixing(self):
+    os.mkdir('audio_files')
+    shutil.copy(test_file('webaudio/audio_files/emscripten-beat.mp3'), 'audio_files/')
+    shutil.copy(test_file('webaudio/audio_files/emscripten-bass.mp3'), 'audio_files/')
+    self.btest_exit('webaudio/audioworklet_params_mixing.c', args=['-sAUDIO_WORKLET', '-sWASM_WORKERS'])
+
 
 class interactive64(interactive):
   def setUp(self):
     super().setUp()
     self.set_setting('MEMORY64')
-    self.emcc_args.append('-Wno-experimental')
     self.require_wasm64()
+
+
+class interactive64_4gb(interactive):
+  def setUp(self):
+    super().setUp()
+    self.set_setting('MEMORY64')
+    self.set_setting('INITIAL_MEMORY', '4200mb')
+    self.set_setting('GLOBAL_BASE', '4gb')
+    self.require_wasm64()
+
+
+class interactive_2gb(interactive):
+  def setUp(self):
+    super().setUp()
+    self.set_setting('INITIAL_MEMORY', '2200mb')
+    self.set_setting('GLOBAL_BASE', '2gb')
diff --git a/test/webaudio/audioworklet_2x_in_hard_pan.c b/test/webaudio/audioworklet_2x_in_hard_pan.c
index 682a6ec053cef..636b44e777b78 100644
--- a/test/webaudio/audioworklet_2x_in_hard_pan.c
+++ b/test/webaudio/audioworklet_2x_in_hard_pan.c
@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <string.h>
-#include <stdio.h>
 
 #include <emscripten/em_js.h>
 #include <emscripten/webaudio.h>
@@ -16,30 +15,41 @@
 
 // Callback to process and copy the audio tracks
 bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, AudioSampleFrame* outputs, int numParams, const AudioParamFrame* params, void* data) {
+#ifdef TEST_AND_EXIT
   audioProcessedCount++;
+#endif
 
-  // Twin mono in, single stereo out
+  // Twin mono in (or disabled), single stereo out
   assert(numInputs == 2 && numOutputs == 1);
-  assert(inputs[0].numberOfChannels == 1 && inputs[1].numberOfChannels == 1);
+  assert(inputs[0].numberOfChannels == 0 || inputs[0].numberOfChannels == 1);
+  assert(inputs[1].numberOfChannels == 0 || inputs[1].numberOfChannels == 1);
   assert(outputs[0].numberOfChannels == 2);
   // All with the same number of samples
   assert(inputs[0].samplesPerChannel == inputs[1].samplesPerChannel);
   assert(inputs[0].samplesPerChannel == outputs[0].samplesPerChannel);
-  // Now with all known quantities we can memcpy the data
-  int samplesPerChannel = inputs[0].samplesPerChannel;
-  memcpy(outputs[0].data, inputs[0].data, samplesPerChannel * sizeof(float));
-  memcpy(outputs[0].data + samplesPerChannel, inputs[1].data, samplesPerChannel * sizeof(float));
+  // Now with all known quantities we can memcpy the L&R data (or zero it if the
+  // channels are disabled)
+  int bytesPerChannel = outputs[0].samplesPerChannel * sizeof(float);
+  float* outputData = outputs[0].data;
+  if (inputs[0].numberOfChannels > 0) {
+    memcpy(outputData, inputs[0].data, bytesPerChannel);
+  } else {
+    memset(outputData, 0, bytesPerChannel);
+  }
+  outputData += outputs[0].samplesPerChannel;
+  if (inputs[1].numberOfChannels > 0) {
+    memcpy(outputData, inputs[1].data, bytesPerChannel);
+  } else {
+    memset(outputData, 0, bytesPerChannel);
+  }
   return true;
 }
 
 // Audio processor created, now register the audio callback
 void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
-  if (!success) {
-    printf("Audio worklet node creation failed\n");
-    return;
-  }
-  printf("Audio worklet processor created\n");
-  printf("Click to toggle audio playback\n");
+  assert(success && "Audio worklet failed in processorCreated()");
+  emscripten_out("Audio worklet processor created");
+  emscripten_out("Click to toggle audio playback");
 
   // Stereo output, two inputs
   int outputChannelCounts[2] = { 2 };
@@ -65,6 +75,13 @@ void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
   // Register a click to start playback
   emscripten_set_click_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(context), false, &onClick);
 
-  // Register the counter that exits the test after one second of mixing
+#ifdef TEST_AND_EXIT
+  // Register the counter that exits the test after one second of playback
   emscripten_set_timeout_loop(&playedAndMixed, 16, NULL);
+#endif
+}
+
+// This implementation has no custom start-up requirements
+EmscriptenStartWebAudioWorkletCallback getStartCallback(void) {
+  return &initialised;
 }
diff --git a/test/webaudio/audioworklet_2x_in_out_stereo.c b/test/webaudio/audioworklet_2x_in_out_stereo.c
index eb51bcdaa9db7..f9a773742812a 100644
--- a/test/webaudio/audioworklet_2x_in_out_stereo.c
+++ b/test/webaudio/audioworklet_2x_in_out_stereo.c
@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <string.h>
-#include <stdio.h>
 
 #include <emscripten/em_js.h>
 #include <emscripten/webaudio.h>
@@ -15,31 +14,41 @@
 
 // Callback to process and copy the audio tracks
 bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, AudioSampleFrame* outputs, int numParams, const AudioParamFrame* params, void* data) {
+#ifdef TEST_AND_EXIT
   audioProcessedCount++;
+#endif
 
   // Twin stereo in and out
   assert(numInputs == 2 && numOutputs == 2);
-  assert(inputs[0].numberOfChannels == 2 && inputs[1].numberOfChannels == 2);
-  assert(outputs[0].numberOfChannels == 2 && outputs[1].numberOfChannels == 2);
+  assert(inputs[0].numberOfChannels == 0 || inputs[0].numberOfChannels == 2);
+  assert(inputs[1].numberOfChannels == 0 || inputs[1].numberOfChannels == 2);
+  assert(outputs[0].numberOfChannels == 2);
+  assert(outputs[1].numberOfChannels == 2);
   // All with the same number of samples
   assert(inputs[0].samplesPerChannel == inputs[1].samplesPerChannel);
   assert(inputs[0].samplesPerChannel == outputs[0].samplesPerChannel);
   assert(outputs[0].samplesPerChannel == outputs[1].samplesPerChannel);
-  // Now with all known quantities we can memcpy the data
-  int totalSamples = outputs[0].samplesPerChannel * outputs[0].numberOfChannels;
-  memcpy(outputs[0].data, inputs[0].data, totalSamples * sizeof(float));
-  memcpy(outputs[1].data, inputs[1].data, totalSamples * sizeof(float));
+  // Now with all known quantities we can memcpy all the data (or zero it if the
+  // channels are disabled)
+  int totalBytes = outputs[0].samplesPerChannel * outputs[0].numberOfChannels * sizeof(float);
+  if (inputs[0].numberOfChannels > 0) {
+    memcpy(outputs[0].data, inputs[0].data, totalBytes);
+  } else {
+    memset(outputs[0].data, 0, totalBytes);
+  }
+  if (inputs[1].numberOfChannels > 0) {
+    memcpy(outputs[1].data, inputs[1].data, totalBytes);
+  } else {
+    memset(outputs[1].data, 0, totalBytes);
+  }
   return true;
 }
 
 // Audio processor created, now register the audio callback
 void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
-  if (!success) {
-    printf("Audio worklet node creation failed\n");
-    return;
-  }
-  printf("Audio worklet processor created\n");
-  printf("Click to toggle audio playback\n");
+  assert(success && "Audio worklet failed in processorCreated()");
+  emscripten_out("Audio worklet processor created");
+  emscripten_out("Click to toggle audio playback");
 
   // Two stereo outputs, two inputs
   int outputChannelCounts[2] = { 2, 2 };
@@ -67,6 +76,13 @@ void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
   // Register a click to start playback
   emscripten_set_click_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(context), false, &onClick);
 
-  // Register the counter that exits the test after one second of mixing
+#ifdef TEST_AND_EXIT
+  // Register the counter that exits the test after one second of playback
   emscripten_set_timeout_loop(&playedAndMixed, 16, NULL);
+#endif
+}
+
+// This implementation has no custom start-up requirements
+EmscriptenStartWebAudioWorkletCallback getStartCallback(void) {
+  return &initialised;
 }
diff --git a/test/webaudio/audioworklet_in_out_mono.c b/test/webaudio/audioworklet_in_out_mono.c
index 56e405d95c2e4..bd76e1fc1c863 100644
--- a/test/webaudio/audioworklet_in_out_mono.c
+++ b/test/webaudio/audioworklet_in_out_mono.c
@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <string.h>
-#include <stdio.h>
 
 #include <emscripten/em_js.h>
 #include <emscripten/webaudio.h>
@@ -16,7 +15,9 @@
 
 // Callback to process and mix the audio tracks
 bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, AudioSampleFrame* outputs, int numParams, const AudioParamFrame* params, void* data) {
+#ifdef TEST_AND_EXIT
   audioProcessedCount++;
+#endif
 
   // Single mono output
   assert(numOutputs == 1 && outputs[0].numberOfChannels == 1);
@@ -29,11 +30,18 @@ bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, Audi
   // We can now do a quick mix since we know the layouts
   if (numInputs > 0) {
     int totalSamples = outputs[0].samplesPerChannel * outputs[0].numberOfChannels;
+    // Simple copy of the first input's audio data, checking that we have
+    // channels (since a muted input has zero channels).
     float* outputData = outputs[0].data;
-    memcpy(outputData, inputs[0].data, totalSamples * sizeof(float));
+    if (inputs[0].numberOfChannels > 0) {
+      memcpy(outputData, inputs[0].data, totalSamples * sizeof(float));
+    } else {
+      // And for muted we need to fill the buffer with zeroes otherwise it repeats the last frame
+      memset(outputData, 0, totalSamples * sizeof(float));
+    }
+    // Now add another inputs
     for (int n = 1; n < numInputs; n++) {
-      // It's possible to have an input with no channels
-      if (inputs[n].numberOfChannels == 1) {
+      if (inputs[n].numberOfChannels > 0) {
         float* inputData = inputs[n].data;
         for (int i = totalSamples - 1; i >= 0; i--) {
           outputData[i] += inputData[i];
@@ -46,12 +54,9 @@ bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, Audi
 
 // Audio processor created, now register the audio callback
 void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
-  if (!success) {
-    printf("Audio worklet node creation failed\n");
-    return;
-  }
-  printf("Audio worklet processor created\n");
-  printf("Click to toggle audio playback\n");
+  assert(success && "Audio worklet failed in processorCreated()");
+  emscripten_out("Audio worklet processor created");
+  emscripten_out("Click to toggle audio playback");
 
   // Mono output, two inputs
   int outputChannelCounts[1] = { 1 };
@@ -77,6 +82,13 @@ void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
   // Register a click to start playback
   emscripten_set_click_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(context), false, &onClick);
 
+#ifdef TEST_AND_EXIT
   // Register the counter that exits the test after one second of mixing
   emscripten_set_timeout_loop(&playedAndMixed, 16, NULL);
+#endif
+}
+
+// This implementation has no custom start-up requirements
+EmscriptenStartWebAudioWorkletCallback getStartCallback(void) {
+  return &initialised;
 }
diff --git a/test/webaudio/audioworklet_in_out_stereo.c b/test/webaudio/audioworklet_in_out_stereo.c
index 107e0638a9e2c..3c41a26c41e4a 100644
--- a/test/webaudio/audioworklet_in_out_stereo.c
+++ b/test/webaudio/audioworklet_in_out_stereo.c
@@ -1,6 +1,5 @@
 #include <assert.h>
 #include <string.h>
-#include <stdio.h>
 
 #include <emscripten/em_js.h>
 #include <emscripten/webaudio.h>
@@ -16,7 +15,9 @@
 
 // Callback to process and mix the audio tracks
 bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, AudioSampleFrame* outputs, int numParams, const AudioParamFrame* params, void* data) {
+#ifdef TEST_AND_EXIT
   audioProcessedCount++;
+#endif
 
   // Single stereo output
   assert(numOutputs == 1 && outputs[0].numberOfChannels == 2);
@@ -29,11 +30,18 @@ bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, Audi
   // We can now do a quick mix since we know the layouts
   if (numInputs > 0) {
     int totalSamples = outputs[0].samplesPerChannel * outputs[0].numberOfChannels;
+    // Simple copy of the first input's audio data, checking that we have
+    // channels (since a muted input has zero channels).
     float* outputData = outputs[0].data;
-    memcpy(outputData, inputs[0].data, totalSamples * sizeof(float));
+    if (inputs[0].numberOfChannels > 0) {
+      memcpy(outputData, inputs[0].data, totalSamples * sizeof(float));
+    } else {
+      // And for muted we need to fill the buffer with zeroes otherwise it repeats the last frame
+      memset(outputData, 0, totalSamples * sizeof(float));
+    }
+    // Now add another inputs
     for (int n = 1; n < numInputs; n++) {
-      // It's possible to have an input with no channels
-      if (inputs[n].numberOfChannels == 2) {
+      if (inputs[n].numberOfChannels > 0) {
         float* inputData = inputs[n].data;
         for (int i = totalSamples - 1; i >= 0; i--) {
           outputData[i] += inputData[i];
@@ -46,12 +54,9 @@ bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, Audi
 
 // Audio processor created, now register the audio callback
 void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
-  if (!success) {
-    printf("Audio worklet node creation failed\n");
-    return;
-  }
-  printf("Audio worklet processor created\n");
-  printf("Click to toggle audio playback\n");
+  assert(success && "Audio worklet failed in processorCreated()");
+  emscripten_out("Audio worklet processor created");
+  emscripten_out("Click to toggle audio playback");
 
   // Stereo output, two inputs
   int outputChannelCounts[1] = { 2 };
@@ -77,6 +82,13 @@ void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
   // Register a click to start playback
   emscripten_set_click_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(context), false, &onClick);
 
+#ifdef TEST_AND_EXIT
   // Register the counter that exits the test after one second of mixing
   emscripten_set_timeout_loop(&playedAndMixed, 16, NULL);
+#endif
+}
+
+// This implementation has no custom start-up requirements
+EmscriptenStartWebAudioWorkletCallback getStartCallback(void) {
+  return &initialised;
 }
diff --git a/test/webaudio/audioworklet_params_mixing.c b/test/webaudio/audioworklet_params_mixing.c
new file mode 100644
index 0000000000000..446888dcea4cc
--- /dev/null
+++ b/test/webaudio/audioworklet_params_mixing.c
@@ -0,0 +1,174 @@
+#include <assert.h>
+#include <string.h>
+
+#include <emscripten/em_js.h>
+#include <emscripten/webaudio.h>
+
+// Tests processing two stereo audio inputs being mixed to a single stereo audio
+// output in process(), then applying a fade from the parameters.
+
+// This needs to be big enough for the stereo output, 2x inputs, 2x params and
+// the worker stack. To note that different browsers have different stack size
+// requirement (see notes in process() plus the expansion of the params).
+#define AUDIO_STACK_SIZE 6144
+
+// Shared file playback and bootstrap
+#include "audioworklet_test_shared.inc"
+
+// Callback to process and mix the audio tracks
+bool process(int numInputs, const AudioSampleFrame* inputs, int numOutputs, AudioSampleFrame* outputs, int numParams, const AudioParamFrame* params, void* data) {
+#ifdef TEST_AND_EXIT
+  audioProcessedCount++;
+#endif
+
+  // Single stereo output
+  assert(numOutputs == 1 && outputs[0].numberOfChannels == 2);
+  int outSamplesPerChannel = outputs[0].samplesPerChannel;
+  for (int n = 0; n < numInputs; n++) {
+    // And all inputs are also stereo (or disabled)
+    assert(inputs[n].numberOfChannels == 2 || inputs[n].numberOfChannels == 0);
+    // This should always be the case
+    assert(inputs[n].samplesPerChannel == outSamplesPerChannel);
+  }
+  // Interestingly, params varies per browser. Chrome won't have a length > 1
+  // unless the value changes, and FF has all 128 entries even for a k-rate
+  // parameter. The only given is that two params are incoming:
+  assert(numParams = 2);
+  assert(params[0].length == 1 || params[0].length == outSamplesPerChannel);
+  assert(params[1].length == 1 || params[1].length == outSamplesPerChannel);
+  // We can now do a quick mix since we know the layouts
+  if (numInputs > 0) {
+    int totalSamples = outSamplesPerChannel * outputs[0].numberOfChannels;
+    // Simple copy of the first input's audio data, checking that we have
+    // channels (since a muted input has zero channels).
+    float* outputData = outputs[0].data;
+    if (inputs[0].numberOfChannels > 0) {
+      memcpy(outputData, inputs[0].data, totalSamples * sizeof(float));
+    } else {
+      // And for muted we need to fill the buffer with zeroes otherwise it repeats the last frame
+      memset(outputData, 0, totalSamples * sizeof(float));
+    }
+    // Grab the mix level parameter and expand it to have one entry per output
+    // sample. This simplifies the mixer and smooths out browser differences.
+    // Output and input buffers are stereo planar, so the mix data just repeats.
+    float* const mixLevel = alloca(totalSamples * sizeof(float));
+    if (params[0].length > 1) {
+      // This is the regular path, one entry per sample by number of channels
+      for (int ch = outputs[0].numberOfChannels - 1; ch >= 0; ch--) {
+        memcpy(mixLevel + ch * outSamplesPerChannel, params[0].data, outSamplesPerChannel * sizeof(float));
+      }
+    } else {
+      // Chrome will take this path when the k-rate parameter doesn't change
+      float singleLevel = params[0].data[0];
+      for (int n = totalSamples - 1; n >= 0; n--) {
+        mixLevel[n] = singleLevel;
+      }
+    }
+    // Now add another inputs with the mix level
+    for (int n = 1; n < numInputs; n++) {
+      if (inputs[n].numberOfChannels > 0) {
+        float* inputData = inputs[n].data;
+        for (int i = totalSamples - 1; i >= 0; i--) {
+          outputData[i] += inputData[i] * mixLevel[i];
+        }
+      }
+    }
+  }
+  return true;
+}
+
+// Grabs the known worklet parameter and fades in or out (depending on whether
+// it's already fading up or down, we reverse the fade direction).
+EM_JS(void, doFade, (EMSCRIPTEN_AUDIO_WORKLET_NODE_T workletID), {
+  var worklet = emscriptenGetAudioObject(workletID);
+  if (worklet) {
+    // Emscripten's API creates these from a C array, indexing them instead of a
+    // name. Chrome and FF work with 0 but Safari requires the correct "0".
+    var param = worklet.parameters.get("0");
+    if (param) {
+      param.setTargetAtTime((param.value > 0.5) ? 0 : 1, 0 /* same as context.currentTime */, 0.5);
+    }
+  }
+})
+
+// Registered keypress event to call the JS doFade()
+bool onPress(int type, const EmscriptenKeyboardEvent* e, void* data) {
+  if (!e->repeat && data) {
+    emscripten_out("Toggling fade");
+    doFade(VOIDP_2_WA(data));
+  }
+  return false;
+}
+
+// Audio processor created, now register the audio callback
+void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
+  assert(success && "Audio worklet failed in processorCreated()");
+  emscripten_out("Audio worklet processor created");
+  emscripten_out("Click to toggle audio playback");
+  emscripten_out("Keypress to fade the beat in or out");
+
+  // Stereo output, two inputs
+  int outputChannelCounts[1] = { 2 };
+  EmscriptenAudioWorkletNodeCreateOptions opts = {
+    .numberOfInputs  = 2,
+    .numberOfOutputs = 1,
+    .outputChannelCounts = outputChannelCounts
+  };
+  EMSCRIPTEN_AUDIO_WORKLET_NODE_T worklet = emscripten_create_wasm_audio_worklet_node(context, "mixer", &opts, &process, NULL);
+  emscripten_audio_node_connect(worklet, context, 0, 0);
+
+  // Create the two stereo source nodes and connect them to the two inputs
+  // Note: we can connect the sources to the same input and it'll get mixed for us, but that's not the point
+  beatID = createTrack(context, "audio_files/emscripten-beat.mp3", true);
+  if (beatID) {
+    emscripten_audio_node_connect(beatID, worklet, 0, 1);
+  }
+  bassID = createTrack(context, "audio_files/emscripten-bass.mp3", true);
+  if (bassID) {
+    emscripten_audio_node_connect(bassID, worklet, 0, 0);
+  }
+
+  // Register a click to start playback
+  emscripten_set_click_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(context), false, &onClick);
+  // And a keypress to do affect the fader
+  emscripten_set_keypress_callback(EMSCRIPTEN_EVENT_TARGET_DOCUMENT, WA_2_VOIDP(worklet), false, &onPress);
+
+#ifdef TEST_AND_EXIT
+  // Register the counter that exits the test after one second of mixing
+  emscripten_set_timeout_loop(&playedAndMixed, 16, NULL);
+#endif
+}
+
+// Worklet thread inited, now create the audio processor
+void initialisedWithParams(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
+  assert(success && "Audio worklet failed initialised()");
+  emscripten_out("Audio worklet initialised");
+
+  // Custom audio params we'll use as a fader
+  WebAudioParamDescriptor faderParam[] = {
+    {
+      // This a-rate (one entry per sample) is used to set the mix level
+      .defaultValue = 1.0f,
+      .minValue = 0.0f,
+      .maxValue = 1.0f,
+      .automationRate = WEBAUDIO_PARAM_A_RATE
+    }, {
+      // This k-rate (one entry per frame) is used just to test
+      .defaultValue = 0.0f,
+      .minValue = -100.0f,
+      .maxValue = 100.0f,
+      .automationRate = WEBAUDIO_PARAM_K_RATE
+    }
+  };
+  WebAudioWorkletProcessorCreateOptions opts = {
+    .name = "mixer",
+    .numAudioParams = 2,
+    .audioParamDescriptors = faderParam
+  };
+  emscripten_create_wasm_audio_worklet_processor_async(context, &opts, &processorCreated, NULL);
+}
+
+// This implementation has no custom start-up requirements
+EmscriptenStartWebAudioWorkletCallback getStartCallback(void) {
+  return &initialisedWithParams;
+}
diff --git a/test/webaudio/audioworklet_test_shared.inc b/test/webaudio/audioworklet_test_shared.inc
index 7077a6cb833be..777f106b1e57c 100644
--- a/test/webaudio/audioworklet_test_shared.inc
+++ b/test/webaudio/audioworklet_test_shared.inc
@@ -5,10 +5,13 @@
 // Helper for MEMORY64 to cast a void* to an audio context or type
 #define VOIDP_2_WA(ptr) ((EMSCRIPTEN_WEBAUDIO_T) (intptr_t) ptr)
 
-// Count the audio callbacks and return after 375 frames (1 second with the default 128 size)
+
+// Count the audio callbacks and return after 375 frames (1 second with the
+// default 128 size).
 //
 // *** Remove this in your own code ***
 //
+#ifdef TEST_AND_EXIT
 volatile int audioProcessedCount = 0;
 bool playedAndMixed(double time, void* data) {
   if (audioProcessedCount >= 375) {
@@ -17,6 +20,7 @@ bool playedAndMixed(double time, void* data) {
   }
   return true;
 }
+#endif
 
 // ID to the beat and bass loops
 EMSCRIPTEN_WEBAUDIO_T beatID = 0;
@@ -28,13 +32,15 @@ EM_JS(EMSCRIPTEN_WEBAUDIO_T, createTrack, (EMSCRIPTEN_WEBAUDIO_T ctxID, const ch
   var context = emscriptenGetAudioObject(ctxID);
   if (context) {
     var audio = document.createElement('audio');
-    audio.src = UTF8ToString(url);
+    // Number() wrapper is a workaround for UTF8ToString() needing a JS number
+    // and from64() not being available in EM_JS macros. Fix in UTF8ToString?
+    audio.src = UTF8ToString(Number(url));
     audio.loop = looping;
     var track = context.createMediaElementSource(audio);
     return emscriptenRegisterAudioObject(track);
   }
   return 0;
-});
+})
 
 // Toggles the play/pause of a MediaElementAudioSourceNode given its ID
 EM_JS(void, toggleTrack, (EMSCRIPTEN_WEBAUDIO_T srcID), {
@@ -50,16 +56,16 @@ EM_JS(void, toggleTrack, (EMSCRIPTEN_WEBAUDIO_T srcID), {
       }
     }
   }
-});
+})
 
-// Registered click even to (1) enable audio playback and (2) toggle playing the tracks
+// Registered click event to (1) enable audio playback and (2) toggle playing the tracks
 bool onClick(int type, const EmscriptenMouseEvent* e, void* data) {
   EMSCRIPTEN_WEBAUDIO_T ctx = VOIDP_2_WA(data);
   if (emscripten_audio_context_state(ctx) != AUDIO_CONTEXT_STATE_RUNNING) {
-    printf("Resuming playback\n");
+    emscripten_out("Resuming playback");
     emscripten_resume_audio_context_sync(ctx);
   }
-  printf("Toggling audio playback\n");
+  emscripten_out("Toggling audio playback");
   toggleTrack(beatID);
   toggleTrack(bassID);
   return false;
@@ -70,26 +76,32 @@ void processorCreated(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data);
 
 // Worklet thread inited, now create the audio processor
 void initialised(EMSCRIPTEN_WEBAUDIO_T context, bool success, void* data) {
-  if (!success) {
-    printf("Audio worklet failed to initialise\n");
-    return;
-  }
-  printf("Audio worklet initialised\n");
+  assert(success && "Audio worklet failed in initialised()");
+  emscripten_out("Audio worklet initialised");
 
   WebAudioWorkletProcessorCreateOptions opts = {
-    .name = "mixer",
+    .name = "mixer"
   };
   emscripten_create_wasm_audio_worklet_processor_async(context, &opts, &processorCreated, NULL);
 }
 
+// To be implemented by the test code, allowing initialised() to be changed.
+EmscriptenStartWebAudioWorkletCallback getStartCallback(void);
+
 // Common entry point for the mixer tests
-int main() {
-  static char workletStack[AUDIO_STACK_SIZE];
+int main(void) {
+  char* const workletStack = memalign(16, AUDIO_STACK_SIZE);
+  emscripten_outf("Audio worklet stack at 0x%p", workletStack);
+  assert(workletStack);
+
   EMSCRIPTEN_WEBAUDIO_T context = emscripten_create_audio_context(NULL);
-  emscripten_start_wasm_audio_worklet_thread_async(context, workletStack, sizeof workletStack, &initialised, NULL);
-#ifndef BROWSER_TEST
-  // Special case: browser tests need to exit instantly, interactive tests need to wait
-  emscripten_runtime_keepalive_push();
+  emscripten_start_wasm_audio_worklet_thread_async(context, workletStack, AUDIO_STACK_SIZE, getStartCallback(), NULL);
+
+#ifdef TEST_AND_EXIT
+   // We're in the test harness and exiting is via playedAndMixed()
+  emscripten_out("In test mode, will exit after 1 second of playback");
 #endif
-  return 0;
+  emscripten_exit_with_live_runtime();
+
+  return EXIT_SUCCESS;
 }