Molecular Acid is an audiovisual sequencer built with Processing.
if you want to play around with it go to molecularacid.netai.net/
This video is a demonstration of the current prototype version.
During the first ~4 minutes basic functionality is explained step by step so if you don't have time to watch the whole video, skip ahead to 5:15 or so, from there on it gets more interesting visually.
What's not explained in the video is how sound is generated: MA sends midi notes and CC to Ableton Live, with each channel in MA controlling a midi track in Live.
Currently the two CC's per channel control in almost all cases filter resonance and frequency within Live's Operator.