The Secret of Monkey Island demo has a boatload of differences from the full game-and the Amiga demo is even different from the original EGA version. This is the full demo, edited down to skip some of the walking-back-and-forth.
Is it just me, or just how it is in this early demo, or maybe this is how the song sounds on the Amiga in the full game, but the melody at 2:08 - 2:15 different than the normal rendition of this song?