Mozart began composing the Requiem during the final months of his life, dying before he completed it. He was 35 years old and was at the very pinnacle of his compositional abilities.
In 1791, Mozart composed portions or all of the Introit, Kyrie, Sequence, and Offertory. A version completed in 1792 by Franz Sussmayr included the Sanctus, Benedictus, and Agnus Dei which he first claimed to have constructed from Mozart’s sketches and later claimed to have written entirely himself. There are other versions constructed more recently, but the Sussmayr version is the most frequently performed.
The Requiem is about 50 minutes in length, and is constructed in eight sections of music, two of which have subsections, for a total of 14 sections of music each with its own character and role.
There are countless uses of portions of the Requiem in film and television soundtracks. Particularly noteworthy (punny!) is its inclusion in a “Simpsons” episode when we learn the back story to Homer’s chess prowess.
The Requiem score calls for soprano, contralto, tenor, and bass vocal soloists, a mixed adult chorus, and an orchestra made up of 2 basset horns (older sibling of the clarinet), 2 bassoons, 2 trumpets, 3 trombones, timpani, organ, and the usual string section of violins, violas, cellos and basses.