Pass all the songs with a gold record on every venue to unlock Cheat 3 Collection. Enter the Cheat 3 Collection on the cheats menu by going to extras and entering the cheats section of the game. Select cheat 3 collection and enter one of the codes displayed on the screen. If done correctly you will hear a sound.

Small Head character - Circle, R2, L2, R1, L1, Down, Down, Up
Glass Character - Down, L2, R1, R2, L1, Circle, Square, Circle
Oil Slick Character - L3, L3, R2, R1, L2, L1, Down, Up
Ice Cream Microphone - Square, Circel, Square, Circle, R2, L2, R1, L1