This is especially caused by Mozart's early and mysterious death at 31 during the composition of this Requiem but also by the unusual circumstances of this anonymously ordered commissional work.
Mozart's widow Constance requested Mozart's students Joseph Eybler and later Franz Xaver Suessmayr to finish the work so that she would not need to return the first tranche but could even claim the final payment of the commission. While Eybler wrote his notes directly into Mozart's score, Suessmayr transferred all notes and completed the work. Since Mozart worked with many scraps of paper of which some were even found in the 1960th, it remains unclear how many of the additions were still drafted by Mozart himself and how much of the work was newly invented by the ones completing his work.
Particularities of this Requiem
Different to other church music in this time, Mozart's Requiem has a small orchestration with missing flutes, oboes and French horns and a dominant four parts choir only. This creates a transparent, serious, low voiced and dark shaded basic mode. Compared to other church music during this time, the Requiem Mass does also not include Arias or any soloist virtuosity.
Development and Finalization
Mozart fully completed the Introitus. From the Kyrie up to the Confutatis, he had completed the voice and some orchestral parts but the Lacrimosa of Mozart discontinues after eight measures. However, other parts of the Requiem are believed based on Mozart's scraps of paper. In the 1960th drafts of the Amen Fugue were discovered that Mozart probably intended to include at the end of the Sequentia. Still, in his manuscript fragment, the sections from the Sanctus onwards are not present.
Mozart's widow Constance facilitated the first public perfomances of this work. Doing this, she faced possible conflicts: One source of conflict was that the piece had been a commissional work which had been paid by an anonymous customer. Another source of conflict was the fact that the work had been completed by other composers. Luckily for her, all could be solved some time later.
The important impact that Constance initiated with her efforts to earn money was that Mozart's Requiem was the first to make its way out of the church and into the concert hall. Later on, this move became considered mandatory for all Requiem renderings. Consequently, we placed it under Symphony.
Mozart's Requiem as completed by Suessmayr is divided into the following 14 movements
I. Introitus (Requiem aeternam, choir and soprano solo)
II. Kyrie eleison (choir)
- Dies irae (choir)
- Tuba mirum (solo quartett)
- Rex tremendae (choir)
- Recordare (solo quartett)
- Confutatis (choir)
- Lacrymosa (choir)
- Domine Jesu (choir with solo quartett)
- Hostias (choir)
V. Sanctus (choir)
VI. Benedictus (solo quartett, then choir)
VII. Agnus dei (choir)
VIII. Communio Lux aeterna (soprano solo and choir).