The text shown above includes the entire text of the Agnus Dei as it normally appears. in his musical setting, Bach, however, omits the last repetition of “Agnus Dei, qui tollis peccata mundi,” and moves immediately into “Dona nobis pacem.” The reason is unclear though we can speculate. Bach may have felt the third statement of that text was redundant, especially after the numerous pleas for mercy found in the extensive Kyrie, and to a lesser extend in the Gloria. A second consideration may have been a musical one: the tone of the last portion, “dona nobis pacem (grant us peace,” is different than the focus on mercy earlier, and Bach may have wanted to enact a dramatic musical change sooner, rather than dwelling further on “mercy.”

The Agnus Dei shows many of the characteristic we associate with Bach’s style in general, including many items also discussed in the St. Matthew Passion.

First, Bach employs two different genres in setting the text of the Agnus Dei. The first portion is really a trio sonata, a genre that combines two melodic lines and continuo accompaniment. One melody line is obviously the solo alto voice, while the other is presented by unison violins.

Second, Bach employs stile nuovo and stile antico (the new style and old style, respectively) in these two movements. The first half (alto solo) is florid, elaborate, and clearly dependent on the continuo line, while the second portion (set for chorus) is more like a Renaissance motet. Although strictly speaking it is a fugue, the continuous imitative entrances and use of the instruments in a purely supportive role; that is, they double and reinforce the vocal parts, but are never independent (except for the timpani, which is still used for emphasis). This is similar to the way instruments were often used during the Middle Ages and Renaissance; even in the generation after Bach, composers such as Haydn and Mozart often used trombones to double the vocal parts, but not as dependent entities. Also, Bach writes this movement in 4/2, a common meter for Renaissance motets (though 4/4 or 2/4 became more popular in later eras).

Third, mood painting was clearly a factor in Bach’s setting. The intimate scoring, G minor tonality, chromaticism, and many “lamenting” appoggiaturas create a feeling of lowliness (in comparison to the Lord’s high stature), sorry (for our sins), pleading (for mercy), and humility (who are we to dare approach the Lord, the almighty?). [An appoggiatura is a type of non-chord tone, meaning it is a dissonant note which does not belong to the chord sounding at the same time in other parts; it is characterized by a leap to the dissonant note, then stepwise motion from the dissonant note to a consonant one, usually in descending fashion.]

Fourth, Bach again reworks material here from previous composition (see further discussion of this under the Gloria above). Two sources serve as the basis for the Agnus Dei. The first is the alto aria from the Ascension Oratorio, which retained vestiges of an earlier Bach work, Cantata No. 29. There are distinct similarities between the melody of “Gratias agimus tibi” from the Gloria, compared to the fugue subject of “Dona nobis pacem.”

Did this mean something to Bach? That is, is this similarity more than coincidence? The text of the first occurrence reads “Gratias agimus tibi propter magnam gloriam tuam” – we give you thanks for your great glory. Here, in the Agnus Dei, the music accompanies the words “Dona nobis pacem” – Grant us peace. Do we gain peace through God’s great glory? Is the musical connection a way for Bach to give thanks for the peace we sought?