Enter codes into the cheats menu under options. Strum every note/chord.

G-Green, R-Red, Y-Yellow, B-Blue, O-Orange

Air guitar
(BY) (GY) (GY) (RB) (RB) (RY) (RY) (BY) (GY) (GY) (RB) (RB) (RY) (RY) (GY) (GY) (RY) (RY)

Bret Michaels Singer
(GR) (GR) (GR) (GB) (GB) (GB) (RB) R R R (RB) R R R (RB) R R R

Easy Expert
(GR) (GY) (YB) (RB) (BO) (YO) (RY) (RB)

Hyperspeed
O, B, O, Y, O, B, O, Y

No Fail (does not work in career mode)
(GR) (B) (GR) (GY) (B) (GY) (RY) (O) (RY) (GY) (Y) (GY) (GR)

Performance Mode
RY, RB, RO, RB, RY, GB, RY RB

Precision Mode
GR, GR, GR, RY, RY, RB, RB, YB, YO, YO, GR, GR, GR, RY, RY, RB, RB, YB, YO, YO