Kyrie

Listeners familiar with Bach’s works might be surprised to find three trombones in the orchestra. It was common in Mozart’s time for trombones to reinforce and double the lower voices of the choir; in fact, trombones make regular appearances in operas and sacred works long before they become part of the standard instrumentation for symphony orchestras.

• Begins with a descending, triadic figure in the first violins, creating a lamenting sound; this is reinforced by the slowly descending baseline, c minor tonality, and andante moderato tempo

• Voices enter in imitation (not yet a fugue) on "Kyrie eleison," spaced only two beats apart initially
• A fugue then develops with the next phrase, with entrances SAT spaced four measures apart; the basses enter just before the tenors, on a countersubject rather than on the fugue subject.
• One further statement (the third) of "Kyrie eleison" occurs with the sopranos now adapting a turn motive from the opening violin passage; this leads to a cadence in G minor, the minor dominant key area; this is a little bit of a surprise, as Mozart’s audiences would have been expecting a move to the relative major in a minor key piece

• Mozart does not disappoint his audience, however, as the music moves immediately in the next measure (m. 33) to prepare the arrival in the relative major key (E-flat major) with the entrance of the soprano soloist
• A soprano solo enters (m. 34) with music which is completely different in character and effect–a strong contrast to the opening, and typical of Viennese Classical form. This passage has an unusually wide range, from A-flat below middle C up two octaves to A-flat. It is gentle and scalar, creating a calming effect.

• The choral voices take up another fugue (similar to the fugue in m. 9) with the return of the words "Kyrie eleison." A ternary effect is thus created, as follows:

The Kyrie closes with a return to the opening string passage (descending triads), enhanced by the choral sopranos on the turn figures, supported by homophonic singing in the lower voices of the choir.