you get to pick your tama's instrument! You only start out with one, but as generations go by you acquire more and more instruments and toys! You can also change their instrument at any time!
I'm running my music star right now along with my v5.5. It's a bit more needy than the 5.5 but it's not as needy as some others. Mine have all gone through alot of neglect and are still alive, so i'd say they aren't too hard!
I'm sure somebody else can explain all the details better! I think there is a music star features topic somewhere on TT aswell...
If you have any questions, feel free to ask! I've played them since they came out. C: