Midvalley the Hornfreak

Midvalley the Hornfreak is a violent musician who is able to use his saxophone, Sylvia, to synchronize sound waves with pain, causing physical damage. He also is capable of neutralizing sounds by playing counter-frequencies. He and his band originally just kill for money until being found by Knives, who kills all except Midvalley. He dislikes both Legato and Knives, which leads him to try to kill Legato, though he is quickly killed himself. Legato uses Midvalley's body to attack Hoppered, and it is buried with his saxophone on his gravestone afterward. He has a smaller role in the anime, mainly acting as Legato's bodyguard until fighting Vash, and killing himself after overloading his saxophone.

(Source: Wikipedia)