Unlockable: All Songs

If you want to unlock every song in the game (which disables the ability to save), head to the game’s title screen and insert the following code on any instrument: Red, Yellow, Blue, Red, Red, Blue, Blue, Red, Yellow, Blue.

To unlock the Gold Fender Stratocaster, complete Solo Tour mode with the guitar.

To unlock a Golden Microphone, score a million points or more in Solo Tour.

To unlock the Silver Fender Stratocaster, complete the Bonus Tour option on Solo Tour with the guitar.

To unlock the "transparent" series of instruments (which gives you a transparent bass, guitar, drum kit and microphone), enter the Hall of Fame on that instrument. So, if you want the transparent bass, enter the Hall of Fame as a bassist.