Tutorial 162: Beat-based Time Shifting

Joe Clay | Feb 8, 2019

I was asked, a while ago, to look into time shifting based on audio. So in this week's After Effects tutorial, we use audio amplitude along with an expression to shift a layer's time. We're using the Timewarp effect for time shifting, since we can change speed pretty easily. We could use time-remapping but that would be more complicated.

To get the audio amplitude, I'm using Trapcode Sound Keys but you can make due using built-in audio effects to pull out specific frequencies. When you use Animation > Keyframe Assistant > Convert Audio to Keyframes, it takes those audio effects into account when determining amplitude. You could also run Convert Audio to Keyframes on a special track you've run through another audio program, like Audition. Of course, Sound Keys is the best way to achieve this effect because it has other options, like falloff, that allow you to fine tune the effect to your taste.

The music used for the beat is: Jesse Warren - Miles Above You.

Expression Code

This is only an example. You'll need to modify what layer you're picking amp from if you're using Sound Keys for example. You'll also need to modify the ease() to match your actual audio amplitude or Sound Keys.

amp = thisComp.layer("Audio Amplitude").effect("Both Channels")("Slider");
ease(amp, 7, 8.5, 100, -400);

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