no1 mentioned there was Multi-Card Download Play.
Well, i've made out some of the Multiplayer options. It's 2-4 Players, no co-op =/
There are 4 game types:
Score (Highest score wins; self explanatory)
# of Hits (Every correct hit on the screen adds +1 to your Score)
# of Accurate/Repeated Hits (Score only adds +1 if you hit accurately or hit a couple in a row, not sure)
Combo (You gain Score according to how many hits you string together, the second you "miss" a beat, your score goes right back to 0 and you start your Score over)
Bonuses Items:
Yes or No (If yes, randomly placed score multipliers appear on the game screen and I'm sure the bonuses are random and Mario like based, as in, if your last place, you'll probably get a 10x multiplier, but if your in first you'd probably get 2x multiplier, anyway thats my guess.