Count Franz von Walsegg’s wife died at the age of 20 in February 1791. To commemorate the first anniversary of her death, he commissioned an Austrian composer to set the Requiem mass to music, possibly to pass off as his own work as he had done with others. That Austrian composer was Mozart.
Mozart set to work, and by the time he died in December 1791 had completed the opening movement (the Introit), detailed drafts of the Kyrie and the sequence Dies irae as far as the first eight bars of the Lacrymosa movement, and the Offertorium.
His widow, Constanze, offered it to one of his pupils to complete, who turned it down saying he wouldn’t dare to complete a work of the master. She approached another of Mozart’s pupils – Franz Xaver Süssmayr – who did so, and handed the completed score to Count von Walsegg. Süssmayr composed a new Sanctus, Benedictus and Agnus Dei as his own contribution to the work.
It’s a piece with a number of stories and myths – one of Salieri as part of Peter Shaffer’s fictional 1979 play Amadeus, but also stories spread by Constanze in hope of generating more interest in the work – that a mysterious stranger commissioned the work, or that Mozart believed he was writing the Requiem for his own funeral. Entertaining, but unhelpful.
As with any incomplete work (look at Mahler 10, or Elgar 3), future composers and musicologists attempt to complete the works using the best knowledge and contemporary context they have. They are many ‘editions’/’completions’ of Mozart’s Requiem by scholars such as Duncan Druce, Robert Levin, and H Robbins Landon.
For me, Richard Maunder’s is the most convincing following the discovery of an Amen fugue for the Requiem, Maunder:
“rewrote the orchestration working from Mozart’s autographs and eliminated Süssmayr’s portions except for the “Agnus Dei” and the ending of the work (“Communio”).
He recomposed the “Lacrymosa” from bar 9 onwards and incorporated a completion of the “Amen” fugue based on Mozart’s sketch.
For his instrumentation, he relied on instances from Mozart’s late operas that he deemed appropriate”,
which to me makes it sound more ‘Mozart’ than Süssmayr – am I right…?
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