MusicVis generates slick animations based on MIDI input. You can see a screenshot of a movie generated by it in the header, and the full video over here. It licensed under the GPL, version 3, so you can modify it however you like, as long as you distribute the source code of your changes with your modified version.
If you wish to compile and run the source code, you’ll need to have Processing, proMIDI, and a graphics card with OpenGL support.
