diff --git a/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java b/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java
index 4fc52c001f..a6b2d9c657 100644
--- a/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java
+++ b/demos/transformer/src/main/java/androidx/media3/demo/transformer/ConfigurationActivity.java
@@ -119,6 +119,7 @@ public final class ConfigurationActivity extends AppCompatActivity {
   public static final int SAMPLE_RATE_INDEX = 1;
   public static final int SKIP_SILENCE_INDEX = 2;
   public static final int CHANNEL_MIXING_INDEX = 3;
+  public static final int VOLUME_SCALING_INDEX = 4;
 
   // Color filter options.
   public static final int COLOR_FILTER_GRAYSCALE = 0;
@@ -165,7 +166,11 @@ public final class ConfigurationActivity extends AppCompatActivity {
     "720p H264 video with no audio",
   };
   private static final String[] AUDIO_EFFECTS = {
-    "High pitched", "Sample rate of 48000Hz", "Skip silence", "Mix channels into mono"
+    "High pitched",
+    "Sample rate of 48000Hz",
+    "Skip silence",
+    "Mix channels into mono",
+    "Scale volume to 50%"
   };
   private static final String[] VIDEO_EFFECTS = {
     "Dizzy crop",
diff --git a/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java b/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
index fb07f429cf..cadf4f14ec 100644
--- a/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
+++ b/demos/transformer/src/main/java/androidx/media3/demo/transformer/TransformerActivity.java
@@ -414,14 +414,29 @@ public final class TransformerActivity extends AppCompatActivity {
       processors.add(silenceSkippingAudioProcessor);
     }
 
-    if (selectedAudioEffects[ConfigurationActivity.CHANNEL_MIXING_INDEX]) {
+    boolean mixToMono = selectedAudioEffects[ConfigurationActivity.CHANNEL_MIXING_INDEX];
+    boolean scaleVolumeToHalf = selectedAudioEffects[ConfigurationActivity.VOLUME_SCALING_INDEX];
+    if (mixToMono || scaleVolumeToHalf) {
       ChannelMixingAudioProcessor mixingAudioProcessor = new ChannelMixingAudioProcessor();
       for (int inputChannelCount = 1; inputChannelCount <= 6; inputChannelCount++) {
-        float[] mixingCoefficients = new float[inputChannelCount];
-        Arrays.fill(mixingCoefficients, 1f / inputChannelCount);
+        ChannelMixingMatrix matrix;
+        if (mixToMono) {
+          float[] mixingCoefficients = new float[inputChannelCount];
+          // Each channel is equally weighted in the mix to mono.
+          Arrays.fill(mixingCoefficients, 1f / inputChannelCount);
+          matrix =
+              new ChannelMixingMatrix(
+                  inputChannelCount, /* outputChannelCount= */ 1, mixingCoefficients);
+        } else {
+          // Identity matrix.
+          matrix =
+              ChannelMixingMatrix.create(
+                  inputChannelCount, /* outputChannelCount= */ inputChannelCount);
+        }
+
+        // Apply the volume adjustment.
         mixingAudioProcessor.putChannelMixingMatrix(
-            new ChannelMixingMatrix(
-                inputChannelCount, /* outputChannelCount= */ 1, mixingCoefficients));
+            scaleVolumeToHalf ? matrix.scaleBy(0.5f) : matrix);
       }
       processors.add(mixingAudioProcessor);
     }