Go to the minigame selection screen in Snide's HQ (needs to be unlocked first) and hit A and B at the same time. If done right, you should be brought to a secret area that the developers probably used to test out the game mechanics. If you try to run out of this area, you will just be warped back to the starting point. So to leave this area, you must reset the game.

If you hold the Z button and slide off of a high ledge, you will fall safely to the bottom without taking any damage.

Once you get a Kong's instrument from Candy's Shop, she mentions that using the instrument will 'deafen' (kill) enemies, and even trigger special events for free when played on its own pad. However, if you're running low on instrument power, and you want to use it to kill the enemies in the vicinity but not trigger the event (i.e. in Angry Aztec, if you want to kill the Kremling outside the temple but don't want the bird to swoop down and pick you up), simply stand on the rim of the pad and play your tune. This will trick the game into allowing you to perform the move for free, but not trigger the event.

Note: This only works when the Instrment Pad is designated for the Kong you're playing as.