The following commands can be entered while in the "SELECT MUSIC" screen.
Code Effect
P,P, while holding G Changes difficulty from BASIC to EXTREME
P, G, G, P Changes guitar mode from default to Bass and Open Pick...
G,G,G Changes the note scroll speed from 1.0 up to 10 (MAX)
Hold start after selecting a music Enters PLAY STYLE MENU
P, P, P, P... Resets all play style changes to default
Select (while holding G) Sorts the music list