At the title screen, press and hold UP, DOWN, LEFT, RIGHT to get to the sound test screen- Choose a song with LEFT or ROGHT on the D-Pad and then press A to listen to it.

GO JAPANESE

For whatever reason you'd want to turn the game language into Japanese, then press UP, RIGHT, DOWN, LEFT, UP, UP, DOWN, DOWN, UP, DOWN, LEFT and RIGHT at the copyright screen. Once the code has been entered correctly the game will reset and the language is Japanese, weee!