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Bosch's Butt Song
It is a known fact that in The Garden of Earthly Delights, by Hieronymus Bosch, on the right panel depicting hell, there is a piece of music painted on someone's butt. For more information on the painting which Bosch painted between 1490 and 1510, see here.
Recently there were some interesting interpretations of the music on the poor man's butt,
https://www.pri.org/stories/2014-02-14/hieronymus-bosch-painted-sheet-music-mans-butt-and-now-you-can-hear-it
https://news.artnet.com/art-world/bosch-butt-song-from-hell-309732
https://www.youtube.com/watch?v=OnrICy3Bc2U
https://www.youtube.com/watch?v=Br3SunLc8zU
Nigel Horne published an interesting and short guide on how to transcribe this medieval notation: The Written Notation of Medieval Music