Go to Extras menu, then Modify Game, and click on Enter Unlock Code.

Password	Effect
Triangle, Square, L1, Triangle, Square, L1, Triangle, Square, L1	Awesome Detection
Square(2), Circle(2), Triangle(2), Square(2)	Performance Mode
Square, L1(2), Square, Triangle, Square, L1(2), Square, Triangle	Select Venue Screen
Triangle, Circle, Square, Triangle, Circle, Square, Triangle, Circle	Stage Mode
Circle, Triangle, Square, Circle, Circle, Square, Square, Circle, Triangle, Square	Unlock All Songs