(Miserere (Allegri) - Wikipedia)Composed around 1638, Miserere was the last and most famous of twelve falsobordone settings used at the Sistine Chapel since 1514. At some point, it became forbidden to transcribe the music and it was allowed to be performed only at those particular services at the Sistine Chapel, thus adding to the mystery surrounding it.
Three authorized copies of the work were distributed prior to 1770: to the Holy Roman Emperor, Leopold I; to the King of Portugal; and to Padre (Giovanni Battista) Martini. However, none of them succeeded in capturing the beauty of the Miserere as performed annually in the Sistine Chapel. According to the popular story (backed up by family letters), fourteen-year-old Wolfgang Amadeus Mozart was visiting Rome when he first heard the piece during the Wednesday service. Later that day, he wrote it down entirely from memory, returning to the Chapel that Friday to make minor corrections.