Here is an experiment made by my fellow colleague and graphic designer Luke White 3rd year GD UCA. He used half of plastic cup with clingfilm over the top, and a small piece of mirror attached to the film. When a laser is pointed at the piece of mirror and music is playing loudly, the bass makes the clingfilm move which makes the laser beam shift, creating a pattern.
http://lukewhite.gdnm.org/
http://www.youtube.com/watch?v=hf_ti2QYwow&feature=BFa&list=LLZt9QK94s8ko&index=2