The Sistine Chapel. Via Wikimedia Commons (public domain).
Gregorio Allegri’s Miserere was the most protected piece in Europe. It was performed only in the Sistine Chapel, only during Holy Week, by the light of candles snuffed out one by one; tradition has it that copying it or carrying the parts out was forbidden on pain of excommunication, and that only a few authorised copies had left in a century, bound for crowned heads. Fame had grown up around that prohibition: half the Grand Tour passed through Rome just to hear it.
In April 1770 a father and son from Salzburg, on tour, also passed through Rome. On Holy Wednesday, 11 April, they attended the service; back at their lodgings, the fourteen-year-old wrote out the whole Miserere from memory. On Friday they returned to hear it again, with the sheet hidden in his hat, to correct the details. It is not a legend: the father, Leopold Mozart, tells it in a letter to his wife dated 14 April 1770, with the pride and caution of one who knows he has contraband at home: we have it, he writes, but we do not wish to let this secret fall into other hands.
What follows dismantles half the myth and makes it more interesting. The excommunication never came: Pope Clement XIV, informed, summoned the boy and, instead of punishing him, decorated him with the Order of the Golden Spur. And the secret, to be honest, did not lie in the notes. The score of the Miserere is a rather simple falsobordone, and in some form was already circulating: the real treasure was the unwritten ornaments the papal singers handed down by voice, the way of embellishing those harmonies that no copy could capture. Wolfgang carried off the only portable thing, and the Vatican knew it: hence, perhaps, the clemency.
One last surprise, for readers who love philology: the celebrated high C of the soprano, the thrill for which the Miserere is still programmed today, Mozart in all likelihood never heard. The early sources do not contain it: scholars trace it to a nineteenth-century transcription error, a wrong combination of two passages that went to print and became tradition. The most secret piece in Christendom reached us through a teenage ear and a misprint: the history of music, as anyone who has read the story of Don Giovanni knows, is made this way too. And the misprint, it must be admitted, is beautiful.