Miserere Mei Deus is Gregorio Allegri's setting of Psalm 51, composed in the 1630s for use in the Sistine Chapel during Holy Week. The Vatican kept the music secret for over a century, which added to its legend, until the young Mozart famously wrote it out from memory in 1770 after hearing it twice. The soaring soprano line and high C that define this climax became its most recognised feature, and recordings since have made it a shorthand online for heaven, purity and transcendent beauty.