This now popular work was commissioned by Franz, Count of Walsegg on the death of his wife in 1791. Franz was a larger than life character who commissioned work from leading composers, usually anonymously, and then asked his court musicians to guess who had written it.
However it was left unfinished when Mozart died in December of that year. Constanze, Mozart’s wife gave the task of completing the score to Joseph Eybler who was able to embellish part-written sections such as the Dies Irea but could not rise to the challenge of composing from scratch. Constanze then asked Franz Xavier Sussmayer to complete the task but his full contribution is still unknown. Sussmayer’s completed score is dated 1792. In the 19th century, Mozart’s Requiem was used at the funeral or memorial services for many leading composers and musicians including Haydn, Beethoven, Schubert, Chopin, Rossini, and Berlioz
This sacred work was composed in 1780 for liturgical use in Salzburg Cathedral and was Mozart’s final choral work composed for the cathedral. The title “de confessore” was not Mozart’s own. It was added to the score later in different handwriting, possibly to distinguish it from Mozart’s previous composition Vesperae de Dominica from the previous year.