There are no "official" cheats for this game, only some glitches. These glitches differ depending on the map and server (if you're playing multiplayer.)
from the main menu enter the cheats menu to enter these codes (legend: R=Red G= Green Y=yellow B=blue O=orange)
additional line 6 effects (music studio): g, r, y, b, r, y, b, g.
Air instruments: r,...