What if one of the most famously guarded pieces of music in history was never really locked in a vault, and the soaring high note that gives listeners goosebumps today was the product of a documented clerical error? This episode traces the strange biography of Gregorio Allegri’s Miserere mei Deus, composed in the 1630s for the candle-extinguishing Tenebrae services in the Sistine Chapel, drawing on Leopold Mozart’s 1770 letters, Charles Burney’s travel diaries, the 1661 Sistine Codex and Robert Haas’s 1932 edition.

We dismantle the legend that a 14-year-old Mozart transcribed the piece from memory after a single hearing, noting that the Academy of Ancient Music in London was already performing it in the 1760s and that Mozart had just visited Padre Martini, who owned an authorized copy. The real secret was never the sheet music but the abbellimenti, the unwritten ornaments passed orally between Sistine singers. Then we follow the chain of transcription errors that culminated in Haas grafting a transposed passage onto the original pitch, rocketing a tenor line into the soprano stratosphere and creating the iconic top C, cemented worldwide by the 1963 King’s College Cambridge recording with boy treble Roy Goodman.

• How falsobordone and three vocal groups build tension toward the nine-part climax of the 14-minute work
• The myth of three authorized copies and why rival choirs found the bare score boring without the oral ornamentation tradition
• The cracks in Leopold Mozart’s account of his son’s feat and the award of the Order of the Golden Spur
• Why William Smith Rockstro transposed the piece up a fourth in 1880 and how Robert Haas failed to notice the key change
• The 2015 Sistine Chapel Choir recording that returned to the 1661 Codex and dropped the top C entirely