Andrew Devis from CreativeCow with a two part tutorial on using audio to control and drive effect perimeters in Adobe After Effects. Andrew does this two ways, one is a more workman like approach while tutorial two has a more elegant approach to it. Watch part one here, and part two here.
The Workmanlike Approach – This is the first of 2 After Effects tutorials which do the same thing but with slightly different methods. This version is the both slightly simpler and quicker method, and is ideal if you are only controlling a couple of items with your audio. Version 2 shows how to keep all the controllers on a single layer and is better suited for more complex projects with many layers, which need good organisation. You will probably find it useful to watch this tutorial first if you are not experienced in using audio and expressions.
