Here are some cheats and tips for the game Ninja Gaiden.
Sound test:
Hold Left + Select + Start + A
+ B when the phrase “Tecmo Presents 1989” appears.
Continue to hold all buttons until the title screen appears in
full. A sound will confirm correct code entry. Press Start
to display the sound test screen. Press Up or Down
to select a sound, A to play a sound, and B to stop
a sound.