Rock Band Codes -

Unlock All Songs
Enter the following code (quickly on drums) at the "Press Start" screen to unlock all songs: Yellow, Red, Blue, Yellow, Yellow, Blue, Blue, Yellow, Red, Blue.

Unlock Instruments
Complete the indicated task to unlock the corresponding instrument:

Gold drum kit - Complete Solo Tour mode on drums under the Medium or higher difficulty.
Gold Fender American Deluxe Stratocaster HSS guitar - Complete Solo Tour mode on guitar under the Medium or higher difficulty.
Gold Fender Bass - Complete Solo Tour mode on bass under the Medium or higher difficulty.
Gold microphone - Complete Solo Tour mode on vocals under the Medium or higher difficulty.
Silver drum kit - Complete the Bonus Tour on Solo Tour mode on drums.
Silver Fender American Deluxe Stratocaster HSS guitar - Complete the Bonus Tour on Solo Tour mode on guitar.
Silver Fender Bass - Complete the Bonus Tour on Solo Tour mode on bass.
Silver microphone - Complete the Bonus Tour on Solo Tour mode on vocals.
Transparent drum kit - Have a PR firm and a set of body guards at the end of Band World Tour to get an invitation for the Moscow Hall of Fame concert. Complete the eight set song list for that concert on the drums.
Transparent Fender American Deluxe Stratocaster HSS - Have a PR firm and a set of body guards at the end of Band World Tour to get an invitation for the Moscow Hall of Fame concert. Complete the eight set song list for that concert on the guitar.
Transparent Fender Bass - Have a PR firm and a set of body guards at the end of Band World Tour to get an invitation for the Moscow Hall of Fame concert. Complete the eight set song list for that concert on the bass.
Transparent microphone - Have a PR firm and a set of body guards at the end of Band World Tour to get an invitation for the Moscow Hall of Fame concert. Complete the eight set song list for that concert on vocals.

Unlocking Different Instrument Icons
You can unlock different colors for your Instrument Icons by beating the Endless Setlist on different difficulties:

Inverse Colors - Finish the Endless Setlist on Medium mode
Gold Icon - Finish the Endless Setlist on Hard mode
Platinum Icon - Finish the Endless Setlist on Expert mode