Music Animation Machine
I was listening to Tommy Emmanuel's rendition of Classical Gas, and got sidetracked to Vanessa Mae's version. My favorite piece of hers is Bach's Toccata and Fugue in D minor, but after that another video caught my attention. It was a scrolling bar score of the piece, created by the Music Animation Machine.
Although they put it in nicer terms, what they have is essentially a visualization for music, and only for MIDI. However, I was taken by the idea, because the mapping from music to visualization is so clear. It is simply a slightly simplified rendition of the music score, and therefore is a homomorphic (I think) function. In this sense, the scrolling bar score is the music, just as any normal score is. With this simplified score though, the structure of the music becomes much clearer, espeically for complex orchestral pieces.
I encourage you to go over and play with the software (which is unfortunately Windows only). You can look at a few videos of what it does first on YouTube, but it's more fun to put in pieces yourself. I particularly enjoyed its output for Beethoven's Pastoral Symphony (the last link), as well as some of Bach's fugues (here and here).