Before anything else, let me just say that the human piano has nothing to do with the human centipede. It doesn't involve stitching people side by side so you can play them and have them bleat out a note when you step on them or something. Rather, it's just a supercut of sorts of different people belting out a single note and then combined later on to come up with something that's nothing short of amazing.
The Human Piano was created by Israeli filmmaker Eran Amir. It seems like a simple project, but it really wasn't. Eran had to go out and record the voices of 300 random people in order to recreate the Super Mario Bros. theme song using nothing but the voices. Did he succeed? Does it sound anything like the actual theme? Check out the clip to find out.