A mysterious messenger, a pouch of gold, and a commission for a mass for the dead: the story behind Mozart's Requiem in D minor sounds like Gothic fiction, and much of it was deliberately manufactured. This episode separates the documents from the myth. The anonymous patron was Count Franz von Walsegg, a wealthy amateur who habitually commissioned works and passed them off as his own, and who wanted a requiem to memorialize his 20-year-old wife Anna. Mozart took half the fee, fully orchestrated only the Introitus, sketched the vocal lines and bass for the Kyrie, Sequence, and Offertorium, and broke off after eight measures of the Lacrimosa before dying on December 5, 1791.

We follow his widow Constanze's scramble to finish the score and collect the second payment: Joseph Eybler's abandoned attempt, Franz Xaver Süssmayr's completion of the L ...