Go to the Shop menu.
Sounds of Mute City: X, X, X, Y, X, X, X, Y, Z, Z, left, right, left, right, left, right
Sounds of Big Blue: Z, left, right, Left, Z, Y, X, Z, left, right, left, right, Z, X, Z, X, Z
This unlocks them to buy, though, for ninety-nine tickets each. I like the default songs and the classic ones about the same. If you're more of a puritan-type gamer, you can beat all the cups on Master instead... I'm on my way to that, but that's because I want the AX cup. I want it badly.