.......On a different note, not really replying to anyone, I just thought up of an interesting idea. May be a little stupid, but what if one player could late "trap notes" which would make you lose points if you hit them. There could be trap notes that look a little different from blast notes, flame notes, (what ever note powerup you have set), and you have to really pay attention to what the blast notes look like. Maybe the player placing trap notes can also send projectiles from time to time. Of course, you can't just spam these "trap notes." If the player trying to get the points gets 4 or 5 stars, he wins, if not and the score is bad, he losses. (Or maybe gold stars and 5 stars since they're so easy to get.)
Of course, now this sounds like a stupid and terrible idea, since it wouldn't work out with the one-track songs (whoops lol) and it just seems kind of weird one person gaining points, and the other not. But I thought this would be some fun gameplay, it was fun to write and think up of.