I thought this was a pretty cool article by Daniel Cook who suggests that you should share your game idea.

http://www.lostgarden.com/2005/08/why-you-should-share-your-game-designs.html

So in the interest of sharing game ideas, here one that I just prototyped:

Sorry about that...Thanks Tom!

Well, at it's basic kernel, maybe. But here are some extensions:
1) Split out several tracks of the song and require the player to use skill shots to hit key notes, crashes, guitar riffs, etc.
2) Maybe a world that's designed more like a parkour level, you see the trail you need to take, but you need to decode the puzzle
3) Time trial, you need to play the song within a certain amount of time and with a certain accuracy...AI attacks you
4) Co-op, each person needs to travel down their own track all while staying in sync to some degree.

Just some brainstorming...