Cheat mode
At the main menu, select "Options", "Cheats", "Enter New Cheat", then enter one of the following codes to unlock the corresponding cheat option:

Performance Mode
Press Yellow(2), Blue, Red, Blue, Green, Red(2).

Hyperspeed
Press Green, Blue, Red, Yellow(2), Red, Green(2).

Auto Kick
Press Yellow, Green, Red, Blue(4), Red. The bass drum pedal will now be played automatically. Note: Enabling this code will disable earning any money after a song has been completed.

Unlock Quickplay
Press Blue, Blue, Red, Green(2), Blue(2), Yellow.

Aaron
Press Blue, Red, Yellow(5), Green.

Nick
Press Green, Red, Blue, Green, Red, Blue, Blue, Green.

Johnny Viper
Press Blue, Red, Blue(2), Yellow(3), Green.

Rina
Press Blue, Red, Green, Green, Yellow(3), Green.

Air Instruments
Press Red(2), Blue, Yellow, Green(3), Yellow.

Invisible Characters
Press Green, Red, Yellow(3), Blue(2), Green.

AT&T Ballpark
Press Yellow, Green, Red(2), Green, Blue, Red, Yellow.

Gem Color
Press Blue, Red(2), Green, Red, Green, Red, Yellow.

Flame Color
Press Green, Red, Green, Blue, Red(2), Yellow, Blue.

Star Color
Press Red(2), Yellow, Red, Blue, Red(2), Blue.

Vocal Fireball
Press Red, Green(2), Yellow, Blue, Green, Yellow, Green.

Always Slide
Press Green(2), Red(2), Yellow, Red, Yellow, Blue.

Extra Line 6 Tones
Press Green, Red, Yellow, Blue, Red, Yellow, Blue, Green.

"Pull Me Under" song
Successfully complete an entire career with any instrument. "Pull Me Under" can be played during the credits. Once done, it will be unlocked.
Thanks CheatsCC