The Shape of Song
Songs are pretty:
What does music look like? The Shape of Song is an attempt to answer this seemingly paradoxical question. The custom software in this work draws musical patterns in the form of translucent arches, allowing viewers to see--literally--the shape of any composition available on the Web.
Neat looking, but since it's limited to MIDI files it's not as much fun as it could be. (Though obviously getting musical information out of audio is super duper hard.)