Melody Pianissima is a ghost of Luigi's Mansion that plays the piano and other instruments and has 100 HP total. She also gives Luigi a quiz on a song from the classic Mario games and if he is wrong, he will have out enter and re-enter and start over. If Luigi is right then he will be able to fight her. Luigi must suck up all the piano notes and she will face down and then is the chance for Luigi to suck her in his Poltergust 3000.
The Butler Shivers seems to have a crush on Melody, but it would appear she has rejected him.