Melody Pianissima, the Beautiful Pianist is the sixth portrait ghost in Luigi's Mansion. She first appears in SMG4: Stupid Luigi's Mansion.
When Luigi eventually found an music room, he tries to play the Mad Piano and gets frightened, until he bumps into Melody. She ask him to play with her, and he agrees, so Melody plays on a piano and Luigi play on a Pingas. He starts having fun with it, only to hit on a wall and accidentally vacuum up Melody. The piano starts going crazy, and Luigi throws the pingas instrument to the other side to distract it while he runs away.
In Mario's Smash Or Pass: All Mario Characters, it reveals that Mario once attempted to "smash" her, but it all came to a tragic end when she refused to sit on his face.