Music Keys are items that appear in Dance Dance Revolution: Mario Mix. Mario and Luigi retrieve these keys, as they give them the power of music. They were safely locked up until Waluigi stole them from Truffle Towers. He only took one for himself, then released each of the other three into different locations; one in the ocean, one in Wario's Carnival, and one inside a giant Freezie. As a result, chaos erupted, forcing the Mario Brothers to save the day once more.