The readings for the 18th Sunday after Trinity are both concerned with the dual birthright of Jesus as the son of David and of God. The Epistle, the very beginning of Paul’s first letter to the Corinthians sets up the tenets of belief for new Christians. The Gospel, from the 22nd chapter of Matthew, is even more central. The trick question from the Saducee brings forth the announcement of the great commandment; later in the reading the question of Christ’s dual birth is raised and not really resolved.
In the previous Leipzig cycle Bach had set definitively the great commandment in the opening chorus of Cantata BWV 77. Here that issue does not really appear. He is much more interested in the idea of Jesus as the son of God and of David. The opening chorus of the cantata BWV 96 deals with this in a most subtle way. The orchestral color is dominated by the use of sopranino recorder. Its patterns clearly are generated from the image that dominates the whole second half of the tune of the morning star. The pastoral element suggested both by the use of the recorder and the use of 9/8 meter refers to the lineage of David. Structurally Bach points the listener in the direction of the beginning of the second half of the tune. The phrase about the morning star contains the rather startling modulation to the dominant that is achieved by a chromatic alteration to the melody, something that Bach seldom does, particularly with these well-known chorale melodies. Clearly he wants us to hear this as the climax of the movement and the most important idea in the piece. The chorale tune is in the alto, doubled by a high trombone, thus allowing the recorder to be heard clearly through the texture.
After an alto recitative comes a tenor aria with flute obbligato. The bonds of affection are clearly characterized by the curious way in which the bass relates to the flute. The “bonding” is even more clearly characterized at the entrance of the voice. This large-scale da capo aria is so congenial in its A section that it keeps its interest not through contrast but intricacy of the motivic relationships. The B section becomes surprisingly intense mainly by the extraordinary ways that Bach keeps tightening the harmonic screws.
After the expansiveness of the tenor aria, the brevity of the bass aria is surprising. It is, however, a marvel. The right, then left motion in the text is simply yet effectively characterized by the oboe choir alternation with the strings. The middle section, which digs even deeper, retains the oboe-string choir alternation in the most subtle way. The B section advances so far in its penetration of the text that a da capo would be regressive. A simple tutti ends the aria. The final harmonization of the chorale is so simple and sturdy that it disguises its extraordinary artfulness, particularly the active and resourceful bass line.