How'd they do this?

I came across this site. It has an audio player on the high-bandwidth version of the site
www.muzak.com
with a graphic equalizer that actually works. Every other graphic equalizer I’ve come across in audio player is never really representative of the music that is playing, it is always some little movie clip on a loop. I thought it was pretty neat.

Does anyone have a tutorial for this? Or just the code to create it?

Cheers