Unlock the following music at the Extras menu by performing the corresponding tasks:

MUSIC - HOW TO UNLOCK
Beach Music - Beat the boss of the Beach section without Super Guide
Cave Music - Beat the boss of the Cave section without Super Guide
Cliff Music - Beat the boss of the Cliff section without Super Guide
Factory Music - Beat the boss of the Factory section without Super Guide
Forest Music - Beat the boss of the Forest section without Super Guide
Jungle Music - Beat the boss of the Jungle section without Super Guide
Ruins Music - Beat the boss of the Ruins section without Super Guide
Volcano Music - Beat the boss of the Volcano section without Super Guide