Which of this istrue?

The patron was Count Franz von Walsegg. He wanted a mass in memory of his wife Anna, who had died in February 1791 at twenty, and he had a habit of buying other people's music to pass off as his own. So the letter and the money came through an intermediary, and Mozart most likely never knew the count's name.

Source: Anton Herzog's memoir, 1839; NMA critical report.

The Magic Flute, premiered on 30 September 1791. The same year also brought La clemenza di Tito for Prague.

That is how Constanze told it, and how the biographer Niemetschek wrote it down in 1798, seven years after the death. There is no other witness. The 'grey messenger' who keeps returning to remind him of the commission comes from the same source. A fine story, but there is no way to check it.

Source: Niemetschek, Life of Mozart, 1798.

Thirty-five. He was born on 27 January 1756 and died on 5 December 1791.

The singer Benedikt Schack told the story in 1827, thirty-six years later. On 4 December, he said, Mozart and three people close to him - Schack himself, his brother-in-law Franz Hofer and the bass Franz Xaver Gerl, who were all singing in The Magic Flute at the time - sang through the finished movements, and at the Lacrimosa Mozart put the music aside. It is the only source, and a late one. It may be true, or a memory that changed over the years.

Source: Schack's obituary, Allgemeine musikalische Zeitung, 1827.

There is no evidence. The physician recorded the cause of death as 'severe miliary fever', which in the language of the time meant a high fever with a rash. Rumours of poisoning went round Vienna in the 1820s, and the elderly Salieri denied them. The story spread widely through Pushkin's short play Mozart and Salieri (1830), then Shaffer's play and the film Amadeus (1984).

Source: Vienna death register, 5 December 1791; Pushkin, 1830; Shaffer, 1979.

There was no music at the funeral on 6 December at St. Stephen's: a short rite by the chapel. But on 10 December a memorial service was held at St. Michael's, arranged by Emanuel Schikaneder - the director of the theatre that had just started playing The Magic Flute. Most likely the Introitus and Kyrie were sung there: no other movements were finished yet, and the music used on the day has not survived. That is the first known performance of the Requiem, if only in part.

Source: A record in the archive of St. Michael's (found by Walther Brauneis in 1991) and a newspaper report of 13 December 1791.

The burial was an ordinary third-class one under Emperor Joseph II's rules: no headstone, several bodies to a pit, no procession to the cemetery. Most Viennese were buried that way. Not a pauper's grave, but the site really was lost; the monument at St. Marx cemetery marks an approximate spot.

Source: St. Stephen's burial register; Braunbehrens, Mozart in Vienna.

In the Lacrimosa, after bar eight, at the words 'judicandus homo reus'. Everything after is Süssmayr.

Unknown. The Lacrimosa manuscript ends after bar eight, and it looks like the end of the work. But the Hostias is written out to the end, with "Quam olim da capo" in the margin, and the order in which he worked on the movements is recorded nowhere. Either leaf could be the last.

Source: Autograph, Austrian National Library, Mus.Hs. 17561.

At the 1958 World's Fair in Brussels someone tore off the corner with one of the three 'Quam olim da Capo' marks. The piece was never found.

Constanze needed the fee, so the work had to be completed. She first turned to Joseph Eybler, who wrote the orchestral parts for a few movements of the day of wrath and then stopped. Franz Xaver Süssmayr, Mozart's twenty-five-year-old pupil and assistant, took over. He completed the Lacrimosa, wrote the Sanctus, Benedictus and Agnus Dei, and brought the opening music back for the ending.

Source: Süssmayr's letter to Breitkopf & Härtel, 1800.

It does, but it is not his. The title page reads 'di me W. A. Mozart 1792': Süssmayr wrote the signature and the date in imitation of his teacher's hand, after Mozart's death. The patron was to receive a work by Mozart, and so he did.

Source: The delivery score; NMA critical report.

On 2 January 1793 in Vienna, at a benefit concert for Constanze. Walsegg performed it as 'his own' only in December 1793.

He did. He copied the score in his own hand and conducted it as its author in Wiener Neustadt on 14 December 1793. But the Requiem had already been heard earlier, on 2 January 1793 in Vienna, at a benefit concert for Constanze. Walsegg was neither the first nor the only one to hear it.

Source: Anton Herzog's memoir, 1839.

Fourteen movements in eight sections. Levin's edition adds a fifteenth - a movement on the word "Amen", built out of a sketch Mozart left unfinished.

Flutes and oboes - the brightest winds in the orchestra. Basset horns take their place, soft and veiled, and that is where the dark sound comes from.

Greek: "Kyrie eleison", "Lord, have mercy". These are the oldest words of the service, older than Latin, and they were never translated.

The Lux aeterna repeats the music of the Introitus and the Kyrie without a single change, only with words about eternal light. The work closes into a circle.

More than 300 ducats - six times what Count Walsegg paid for the whole work. The benefit concert for Constanze was arranged in Vienna by Baron Gottfried van Swieten, a patron of music who supported the family after Mozart's death. For a widow with two small sons it was money she could live on.

Constanze spoke of the scraps in 1826: after Mozart's death a few slips of paper with music were found on his desk, and she gave them to Süssmayr. She did not know what was on them, and the scraps themselves have not survived. Süssmayr also completed an unfinished horn concerto from Mozart's notes, so the story is plausible. But what in the Sanctus or Agnus Dei is Mozart's cannot be checked.

Source: Maximilian Stadler, from Constanze's account, 1826; NMA critical report, 2007.

The opposite. In 1825 the composer and music theorist Gottfried Weber wrote in the journal Cäcilia that most of the Requiem was not Mozart's. Beethoven read the article pencil in hand and answered briefly in the margin: "you arch-ass" and "you double ass". His copy of the journal is in the Library of Congress.

Source: Beethoven's annotated copy of Cäcilia, 1825, Library of Congress.

True. Chopin died in Paris in 1849 and asked for Mozart's Requiem at his funeral. Women were not then allowed to sing in parish churches, and the archbishop agreed only on condition that the singers were not seen. So at the Madeleine the female soloists, among them the opera singer Pauline Viardot, Chopin's friend, were placed behind a black curtain. Chopin's own music is here to listen to as well: his Piano Concerto No. 1.

Source: Accounts of the funeral of 30 October 1849 in Chopin biographies.

50 ducats - exactly what Count Walsegg paid Mozart for the commission in 1791. Since then the manuscript of the Requiem has been kept in Vienna, today in the Austrian National Library.