The Shape of Song is web-based software by New York-based digital artist Martin Wattenberg that has its own unique way of artistically interpreting MIDI files. You can load any MIDI song you can find on the Web into the interface (that's "Eleanor Rigby" by the Beatles pictured above), or pick one of the many songs already in the site's 648-piece repertoire, and it will visualize it for you by drawing translucent arches that correspond with various parts of the music.
Too bad you can't hear the music while it's doing the analyzing and drawing. Guess that will be coming in version 2.0.
The Shape of Song [Turbulence.org]