Peter Aidu performs Steve Reich's Piano Phase. Normally played by two pianists, "Piano Phase" involves playing the same short melody simultaneously on two pianos so that, over time, one player slides out of phase with the other. Aidu's not the first person to play the piece solo, but it's the first one I've seen on video. (An mp3 of the performance is available at the Internet Archive.)

[via Super Colossal]