Rayman Raving Rabbids

Unlock music tracks by completing all four minigames on a level. Here are the respective levels for each music track:

Level 1 - Misirlou
Level 3 - Good Time
Level 5 - Girls Just Want To Have Fun
Level 7 - Hip Hop Hooray
Level 9 - La Bamba
Level 11 - Dark Iron Bunnies Track
Level 13 - The Butcher Deejay Track
Level 14 - Ubisoft Montpellier Choir

WARNING: There is a glitch that can cause your save data to 'forget' that you unlocked a music track! Once you have finished a level and return to your cell, you MUST LEAVE AGAIN BEFORE TURNING OFF THE GAME or it will not save the fact that you unlocked the music track. It is a good idea each time you return to your cell to first check the jukebox to make sure you have them all so far, and then leave the room ("Take More Tests") before you turn off the game. Basically, never quit after the fourth minigame (when the music track unlocks) before exiting your cell to go to the next level.