You must have a key to do this trick. Once you reach a boss, press start and select the key. From the middle of the screen, walk left and down and rapidly press 'A'. It will say ''Thing gives you Invisible Potion. Press start and you'll be at a scrambled screen. Wait a moment and you'll be at the staircase for the next area. Just DO NOT do this on the final boss, or the game will freeze.

Quickly press Select twice to pause and unpause the game, and the sound will be gone. To turn on the sound you have to run into a wall and then pause and unpause the game.