Hieronymus Bosch is already renowned for his symbolically grotesque scenes, but this video has found a hilarious little secret in one of his most famous works. Amelia, a blogger and self-described “hard-of-hearing music and information systems double major,” went viral for a video in which she transcribes and records a 600-year-old musical piece found in Bosch’s “Garden of Earthly Delights,” a painting he’d done back in the 15th century. The shocker? The notes were written on a tortured sinner’s butt.

While inspecting the minute details of Bosch’s painting, Amelia and her friend stumbled upon this poor guy depicted in the last panel of the whole triptych, which represents Hell and its various torture methods. The sheet music is clearly inscribed across his backside, making it possibly the oldest butt song in history yet. “I decided to transcribe it into modern notation, assuming the second line of the staff is C, as is common for chants of this era,” – said Amelia.

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