The composer died mid-score; his pupil finished it secretly

The Midnight Commission

In the summer of 1791, a stranger in gray appeared at Wolfgang Amadeus Mozart's Vienna apartment with an anonymous commission: compose a Requiem Mass, no questions asked. Mozart, perpetually in debt and never one to refuse paid work, accepted the job for 50 ducats. The client was Count Franz von Walsegg, a minor nobleman who regularly commissioned works and passed them off as his own compositions at private concerts—his late wife had died in February, and he wanted a memorial Mass he could claim as his tribute. Mozart never learned the count's identity. By autumn, as he worked feverishly on The Magic Flute and La clemenza di Tito, the Requiem remained unfinished. His health collapsed in November—whether from rheumatic fever, kidney disease, or trichinosis remains disputed—and he died on December 5, 1791, at age 35, with only the opening movements complete.

The Student Steps In

Franz Xaver Süssmayr, a 25-year-old composer who had been Mozart's pupil and copyist, inherited an impossible task. Mozart's widow Constanze faced financial ruin if she couldn't deliver the completed work and collect the commission's second half. Süssmayr had watched Mozart sketch ideas, heard him sing passages at the keyboard, and copied out instrumental parts during the months of composition. Working from Mozart's detailed "Introitus" and "Kyrie," skeletal vocal parts for the "Dies irae" through "Hostias," and scattered scraps of notation, Süssmayr composed entire sections outright: the "Sanctus," "Benedictus," and "Agnus Dei" bear almost no Mozart material. He orchestrated the incomplete movements, invented transitions, and even recycled Mozart's opening "Introitus" music for the closing "Lux aeterna"—a symmetrical choice that felt religiously appropriate. The completed manuscript carried only Mozart's name when Constanze delivered it in 1792, and Count von Walsegg conducted it as his own composition at a December memorial service, fooling exactly no one.

The Handwriting Evidence

For decades the manuscript fooled scholars more successfully than it fooled the count's neighbors. The original score shows three distinct hands: Mozart's rushed, abbreviation-heavy autograph in the early movements; Süssmayr's careful completion of the vocal lines; and Süssmayr's full orchestration filling the later pages. Mozart had written the "Introitus" and "Kyrie" in full score, then switched to a shorthand method for the sequence movements—vocal parts and figured bass only, expecting to orchestrate later. Süssmayr's additions show competent but less inspired craftsmanship: his "Sanctus" fugue lacks Mozart's contrapuntal daring, and his orchestration leans on predictable doublings. Yet he captured something essential. The "Lacrimosa" breaks off after eight bars of Mozart's handwriting; Süssmayr's completion follows Mozart's harmonic logic so closely that the seam nearly disappears. Constanze later admitted the collaboration to publishers, but only after the work had achieved such fame that the truth couldn't diminish it. The Requiem had premiered publicly in January 1793 at a benefit concert for Mozart's family, and Vienna wept.

The Eternal Question

No classical work lives more thoroughly in the space between authentic and apocryphal. Modern scholars have proposed alternative completions—editions by Richard Maunder, Robert Levin, and Duncan Druce attempt to separate Mozart's DNA from Süssmayr's, sometimes replacing entire movements—but Süssmayr's version remains the standard in concert halls and recordings. Why? Because Süssmayr was there. He heard Mozart's intentions in real time, absorbed his working methods, and made choices the dying composer might have endorsed. The Requiem's power survives its hybrid authorship: the "Dies irae" still blazes with apocalyptic fury, the "Recordare" still aches with plea and hope, and the "Lacrimosa" still ranks among music's most devastating expressions of mortal grief. When the Requiem played at Mozart's own memorial service in December 1791—incomplete movements performed, others left silent—the congregation heard a composer mourning his own death. That the work was finished by a student's hand doesn't diminish the ghost it conjures. Every performance since has been a séance.