Pass all the songs with a platium record on every venue to unlock Cheat 4 Collection. Enter the Cheat 4 Collection on the cheats menu by going to extras and entering the cheats section of the game. Select cheat 4 collection and enter one of the codes displayed on the screen. If done correctly you will hear a sound.

Tough Audio Crowd - Circle, L1, L2, R1, R2, Right, Right, Down
Pirate Crowd - Down, L2, L2, R2, R2, Square, Circle, Square
Robot Crowd - L3, Down, Down, R1, Circle, Square, Circle, Square
Zombie Crowd - Square, Square, Circle, Circle, Up, Right, Right, Up
Alien Crowd - Up, Up, Down, Circle, Circle, L2, R2, Square