Getting a flash animation to respond to audio

Right - time for a new project…
After playing around with http://www.kirupa.com/developer/actionscript/microphone.htm and creating an animation that responds to the volume of your voice.
I’d be interested in knowing whether there is a way of doing something similar but the animation ‘responds’ to an audio track - a piece of music. It could react to either the beat or the volume.
Any ideas?