Anyone can listen to music, but how can you see it? The Music Animation Machine plays music (ancient MIDI files) and displays it in real-time. On the vertical are notes and time runs on the horizontal. Here's Debussy's classic Clair de lune, otherwise known as that song from the Ocean's 11 through 13 soundtrack, where they all gather at the fountain and give a nod of recognition to each other.
Naturally, all I can think of as I watch this is the introduction to Peter and the Wolf.