Hold the mouse on the grey side to shut your mouth and let go to sing. You get a point if you close or open your mouth at the right time. (You can also use space.)
Credit to Nintendo. Go buy rhythm heaven if you haven't already. I own a Jap. copy and it's one of the best DS games out there. It is incredibly underated and has 2/3 sequals one of which is japan exclusive. (Dangit The best +!)
