You can easily sync your effects and animations with audio in Adobe After Effects. This can be done by extracting keyframes for the volume of the audio clip and using simple expressions to use these keyframes to drive any effect parameter or layer property you want.This technique is very easy to do and opens up the possibilities to create amazing music visualisations or simplify a lot of common tasks. For example, I used it to animate the opening/closing mouth for the puppet in my After Effects Puppet Tool tutorial .
I animated the mouth to open in sync with the audio to make it look like a South Park character talking. I did not want to animate the mouth by hand because it would have been much too tedious and decided to use the Audio to Keyframes conversion in After Effects to make this job a lot easier for me. This tutorial will take you through that process.
Import the image of the open mouth into your project and place it in your composition, on top of the cutout layer.
Scale it down and position it so it sits precisely over my closed mouth. If you toggle the visibility of the mouth, it should look as if your puppet was talking.
Notice that the edges of the mouth are fairly harsh. While you can use masks to soften the edges, a much simpler way is to use the Matte Choker effect. Apply the Matte Choker to the open mouth layer and increase the Choke as well as the Geometric Softness to smoothen out the edges a bit more.
This will blend the mouth more cleaner with the cutout image and instantly look more realistic. Well, as realistic as you get with puppets!
Now it's time to extract the keyframes from our audio clip!