Instructions
Go to "Extras" from the "Rock Band 2" main menu.
Select "Modify Game" from the "Extras" menu.
Select "Enter Unlock Code." You will be prompted to enter and unlock code with your guitar or drum set.
Enter "Red," "Yellow," "Blue," "Red," "Red," "Blue," "Blue," "Red," "Yellow" and "Blue" on your instrument.
Select "Continue." An "Unlock all songs" option appears in the modifier list.
Select "Unlock all songs" from the list.