pound on all the instruments till the play the mario theme song. Melody will then show up and ask you a question about a piece she played. if you get it right she will fire music sheets at you. Suck them up then shine the light on her when she pounds on the piano. do it fast or she will send out more music sheets to murder you. after you shine the light on her just suck her up.

PS if you get the question wrong she will disapear and you will have to leave the room and start over.