Playing around in Processing. The balls are inspired by Loco Roco, and the music is Mr Scruff (buy his music today).

The animation itself didn't take very long - the hard part of this was getting the sound library (Minim) to let me do the sound spectrum stuff in non-realtime (as rendering out to frames slows things down a lot). In the end I had to save out the byte data to a file, so I could then read it back at a leisurely pace.