To enter the notes go to 'Options' and select 'Cheat' and enter the code you want to enable. You have to strum as you press the buttons in the code or if two buttons are indicated they must be pressed together as you strum as they represent one cord.
R = Red, B = Blue, G = Green, Y = Yellow, O = Orange
Unlock ALL Songs:
Press YO, RB, RO, GB, RY, YO, RY, RB, GY, GY, YB, YB, YO, YO, YB, Y, R, RY, R, Y, O.
Press O, B, O, Y, O, B, O, Y.
Unlock Performance Mode:
Press RY, RB, RO, RB, RY, GB, RY, RB.