Keyframe Editing can be a time consuming affair in After Effects. This is particularly the case when those Keyframes are part of some experimental/conceptual composition or when consistent timing is important (music videos for example).
This method is a great time saver, and is also very simple to apply. I don’t count it will get you through some dark and lonely nights at the computer screen as it has me.
To begin, we need a Comp that contains an Audio Track. This can be Music, Dialogue or Effects. For this Demo I’m using a piece of Music.
Step – 1: Create of open a Comp
Make sure the comp has a Layer that contains your chosen Audio Source.
Now After Effects isn’t great at allowing you to work with Audio, however we can look at the Audio Waveform.
To see the Waveform in the Comp timeline press L twice.
Notice all those peaks?
Step – 2: Convert the Audio to Keyframes
In order for the Audio Waveforms to be able to be used to influence the Properties of other layers, they must be re-created as Keyframes via an Audio Amplitude layer.
To do this, select the layer containing your audio and choose Animation > Keyframe Assistant > Create Audio to Keyframes. Then wait until a new Red coloured layer appears in the Comp Timeline named “Audio Amplitude”.
Step – 3: Utilise the Audio Amplitude
Using the “Uber Key” (press U twice) to reveal all the active properties of the Audio Amplitude.
Notice all the Keyframes. If you look at these Keyframes in the Graph Editor you will see that they match the Audio Waveform we looked at in Step 1.
Select and Property from any other Layer. In this case I’ve chosen the Opacity (T) of a Text Layer.
Hold down Alt and CLICK on the Properties Time Vary Stopwatch, to reveal the expression editor.
Drag the Pickwhip icon from the layers Opacity property over to one of the Audio Amplitudes “Slider” properties.
Play the Comp and the Opacity of the layer will follow the timing and intensity of the Audio track.
Step 4: Increase the Amplitude
The animated opacity may not vary as much as you had hoped, often due to the low dynamic range of the original Audio Levels.
Double Click on the Expression Formulae written next to the Opacity property. Here you can multiply the effect of the Audio Amplitude in the expression by Multiplying the values. Type * (asterisk) and a multiply value (*2 for double, *3 for Treble or *0.5 for Half etc).
Easy and effective every time, try it on a few more properties.