When you are on the title screen, you should see a list of several things to do on the game. Go to the settings place. Once there you will see "cheats". Once you see "cheats" enter the following codes by pressing the G (Green), R (Red), Y (Yellow), B (Blue) buttons corresponding to the cheat. There is no need to strum while doing it.
|GRYBRYBG||Extra Line 6 Tones|
|RRRBBGGY||Always Drum FIll|