It takes just the first twelve bars of the opening movement to get a strong concept of the writing Mozart is about to use in his Requiem. The strings begin with what can be crudely, but fairly accurately, as an Oom-Pah figure. This figure, and variations of it, appear throughout the work. In later movements Mozart alters the amount of notes the violins play in response to the strong ‘on the beat’ presented by basso.
The Bassoon enters in measure 1 with melodic materiel that prepares us for the entrance of the choral parts, seven bars later. In measure 2, the basset horn (An instrument similar in tone to an ‘A’ Clarinet) begins a fugue on the same melody. By the fourth measure both Bassoons and Basset Horns are involved in this fugal counterpoint. These are the only woodwind instruments Mozart makes use of in the Requiem, and I found it quite interesting to note that he uses only the lower and mellow woodwind instruments and ignores the generally common flute and oboe, perhaps he felt they were too bright in timbre for such a sombre composition.
Just before the choral parts begin, Mozart briefly airs the three trombones, two trumpets and timpani. I found it very interesting that on the score I used for this study, the trombone parts do not have their own staves, instead are placed wherever it is possible. At some points they appear on the choir staves, and in the trombone solo in the Tuba Mirum the part is scored on the Bassoon staff.More often than not the trombones were scored on the trumpet and timpani staves, which I found very odd as it reduced the occasions when those instruments would be used together.
I noticed a few common practises with his writing for the choir. Firstly, as was set out from the very start by the winds, writing in the style of a fugue was very common, and very effective in creating interest for the vocal lines. Mozart also makes use of repetition between the male and female voices, almost like a call and response. These two compositional tools ensure that on the occasions that he does write the voices as tutti chords, it really hits you.
The other thing from the vocal writing that I really noticed was that it was fairly rare for a vocal part not to be doubled by at least one of the instruments in the ensemble. This must make it much easier for the choir to sight read.
I found his writing for the choir of great interest as I’m currently workshopping a choral piece. I had gone to some effort to give clues prior to entries so the singers knew each new starting tone, but I hadn’t put any real thought into making use of the accompaniment to achieve this. Definitely something I will think about in future compositions.