Surf Harp

"'I said a harp, harp, harp. Harp is the word.'""-'Surfin' Harp', by the Dustmen"The Surf Harp is the third Instrument of the Sirens, found in Angler's Cavern after defeating the Angler.

Contrary to its name, it does not allow Marty to learn Surf. It does, however, have a pretty haunting tone, if you ask MeccaPrime.