One section of Hieronymus Bosch's massive triptych The Garden of Earthly Delights depicts a hellish chorus singing a song painted on the buttocks of a sinner. Now a musician has transcribed it into modern notation for our asinine listening pleasure.
Amelia, a music and information systems student at Oklahoma Christian University, decided to figure out what the song painted on this fellow's ass sounded like. She assumed that the second line in the staff was a C, which she says was common for chants of the era. (The Garden of Earthly Delights was completed sometime around the year 1500.) Since the rightmost panel of the triptych, where the butt song is found, is meant to represent Hell, Amelia calls this the literal "butt song from hell."
You can listen to her rendition of the tune, played on the piano, on her Tumblr—but also be sure to check out Tumblr user wellmanicuredman's choral arrangement, in which most of the lyrics are, simply, "the butt song from hell." You'll feel like an ass if you don't.
Update: Thanks to commenter regis, here's another version, by Kathryn Tewson.