A note from the PianoGuys: "The pianos will play...when the Guys are away! The pianos are REALLY doing this, no trick photography. This was accomplished with amazing MIDI programming by Craig Knudsen on his Yamaha Disklavier! Note that special codes can move the keys on the Disklavier without generating sounds like normal notes played on the player piano, allowing for these fun patterns and effects on the keyboard."
The things technology can do for us.