Wolfgang Amadeus Mozart (27 January 1756 – 5 December 1791), baptised as Johannes Chrysostomus Wolfgangus Theophilus Mozart, was a prolific and influential composer of the Classical era.
Mozart showed prodigious ability from his earliest childhood. Already competent on keyboard and violin, he composed from the age of five and performed before European royalty. At 17, he was engaged as a court musician in Salzburg, but grew restless and travelled in search of a better position, always composing abundantly. While visiting Vienna in 1781, he was dismissed from his Salzburg position. He chose to stay in the capital, where he achieved fame but little financial security. During his final years in Vienna, he composed many of his best-known symphonies, concertos, and operas, and portions of the Requiem, which was largely unfinished at the time of his death. The circumstances of his early death have been much mythologized. He was survived by his wife Constanze and two sons.
He composed over 600 works, many acknowledged as pinnacles of symphonic, concertante, chamber, operatic, and choral music. He is among the most enduringly popular of classical composers, and his influence on subsequent Western art music is profound; Beethoven composed his own early works in the shadow of Mozart, and Joseph Haydn wrote that "posterity will not see such a talent again in 100 years.

The Requiem Mass in D minor (K. 626) by Wolfgang Amadeus Mozart was composed in Vienna in 1791 and left unfinished at the composer's death on December 5. A completion dated 1792 by Franz Xaver Süssmayr was delivered to Count Franz von Walsegg, who had anonymously commissioned the piece for a requiem mass to commemorate the February 14 anniversary of his wife's death.
The autograph manuscript shows the finished and orchestrated introit in Mozart's hand, as well as detailed drafts of the Kyrie and the sequence Dies Irae as far as the first nine bars of "Lacrimosa", and the offertory. It cannot be shown to what extent Süssmayr may have depended on now lost "scraps of paper" for the remainder; he later claimed the Sanctus and Agnus Dei as his own. Walsegg probably intended to pass the Requiem off as his own composition, as he is known to have done with other works. This plan was frustrated by a public benefit performance for Mozart's widow Constanze. A modern contribution to the mythology is Peter Shaffer's 1979 play Amadeus, in which a mysterious messenger orders Mozart to write a requiem mass, giving no explanation for the order; Mozart (in the play) then comes to believe that the piece is meant to be the requiem mass for his own funeral.
The Requiem is scored for 2 basset horns in F, 2 bassoons, 2 trumpets in D, 3 trombones (alto, tenor & bass), timpani (2 drums), violins, viola and basso continuo (cello, double bass, and organ). The vocal forces include soprano, contralto, tenor, and bass soloists and an SATB mixed choir.