Convert Audio to Keyframes in After Effects

Creating audio-reactive animations in Adobe After Effects begins with translating your sound file into usable animation data. This guide explains how to convert audio amplitude into numerical keyframes using After Effects' native tools, isolate frequency channels, and link those values to layer properties like scale, opacity, and position using simple expression pick-whipping.

1. Import and Add Audio to the Timeline

  1. Import your audio file (WAV or MP3 format is recommended) into your After Effects project.
  2. Drag the audio file into your active composition timeline.

2. Run the Keyframe Assistant

  1. Select the audio layer in the timeline panel.
  2. Right-click the layer, navigate to Keyframe Assistant, and click Convert Audio to Keyframes.
  3. After Effects will analyze the audio waveform and generate a new Null layer named Audio Amplitude.

3. Understand the Audio Amplitude Layer

Select the newly created Audio Amplitude layer and press U on your keyboard to reveal all generated keyframes. You will see three slider controls under the Effects panel:

  • Left Channel: Amplitude keyframes for the left audio channel.
  • Right Channel: Amplitude keyframes for the right audio channel.
  • Both Channels: Combined amplitude data representing the total volume.

For most standard animations, you will link your visual properties to the Both Channels slider.

To make a visual layer react to the music:

  1. Select your target visual layer (such as a shape, text, or solid) and reveal the property you want to animate (for example, press S for Scale or T for Opacity).
  2. Hold Alt (Windows) or Option (macOS) and click the stopwatch next to the property to open the expression field.
  3. Locate the spiral Expression Pick Whip icon next to the property expression field.
  4. Click and drag the pick whip directly onto the Slider property inside the Both Channels effect on the Audio Amplitude layer.
  5. Release the mouse. Your property is now driven by the audio volume.

5. Calibrate the Reaction Range

Raw audio amplitude numbers typically range between 0 and 50, which may not match your target animation values (such as standard scale percentages). You can adjust this directly in the expression box using the linear() method.

Replace the generated expression on your target property with:

audioLevel = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
minAudio = 0;
maxAudio = 30;
minProperty = 100;
maxProperty = 150;

linear(audioLevel, minAudio, maxAudio, minProperty, maxProperty);

Adjust minProperty and maxProperty to control the minimum and maximum size, opacity, or position your layer reaches when the audio hits its quietest and loudest peaks.