Synthesia Mac

Synthesia is a game that teaches you to play the piano using falling notes. No sheet music reading is required. With it, you can:

Learn to play songs using a musical keyboard connected to your computer.
Keep track of your progress in every song with per-song scoreboards.
Slow, fast-forward, and rewind songs while learning new parts.
Practice left and right hand parts together or separately.
Try out any MIDI file you can find on the Internet.
Use it on either your PC or Mac.

It's not done yet, but I'm working hard to finish it. Don't let that stop you though. You can always download the latest version and try it out.