The festival of the birth of John the Baptist was celebrated in 1724 between the 2nd and 3rd Sundays after Trinity. The reading was transferred to the second Sunday in Advent in the new prayerbook. The cantata written for that day is Bach's La Mer: both verbally and musically, water imagery permeates each movement. What is remarkable is that rather than becoming merely an attractive tone poem, the music goes deeper and deeper into this complex story.
The cantata is based on the melody "Christ unser Herr zum Jordan kam." The shape of Luther's tune is significant. The Stollen (first section) is typical, two contrasting phrases repeated. It is the Abgesang (second section) that not only is longer than most, but is unusually shaped. Five phrases build to a climax in the third phrase. The fourth phrase not only cadences but lets down the tension. The fifth phrase is not only unexpected but a full octave higher in range than the previous cadence. This unexpected and intense coda colors the whole mood of the chorale.
Bach sets the first verse as an intense and imaginative seascape. In this work the tenors sing the chorale tune and are submerged beneath the sopranos and altos and most of the string texture. The principal theme is in two parts: a stern, dotted note figure depicting the wild man in lion skins and stormy water music. Two other subjects appear in tandem with the second subject. The combination of all of this material gives an unusual richness to the texture. The relative rigidity of the phrasing of the first subject with the flexibility of phrase length of the second gives a kind of plasticity to the continuity that is useful for such an irregular chorale tune. Bach is, as usual, canny in his solution to potential balance problems with the low-lying chorale tune by thinning out the texture for the most part to the solo concertante violins and continuo when the chorus is singing. The shape of the Abgesang is marvelously achieved. The natural climax of the third phrase is set up with an unusually long orchestral interlude using only the second subject and its related themes. The fourth phrase is allowed to wind down and what sounds like a recapitulation of the opening material is played. In the midst, the last phrase is declaimed, first time that the chorus is accompanied by the full orchestra.
The text of the bass aria exhorts us to action, but the music is of a more intimate nature. The bass line burbles along amiably and the whole character is of greatest contrast to the stormy grandeur of the chorus. Notice how the rhythmic figure which permeates the A section is softened by the more conversational tone of the B section.
The tenor recitative and aria enter into areas of rather complex dogma. We should remember that this festival day is only about four weeks past Whitsunday. The imagery of both the founding of the church and speaking in tongues is implied here. The storminess of the opening resumes, but with even more intensity and vigor. The tenor declaims the text, at the top of his range, and with an heroic athleticism against the bounding solo violins. The leapfrogging upward arpeggios of the violins become sweet floating descending figures at the mention of the dove.
This reference to the recent past in the tenor aria is no accident. The similarity of the following alto aria and the tenor aria of BWV 2 (written two days earlier!) is so striking both in mood and the very quality of their melodies, that one must presume that Bach wants us to hear these pieces not only individually but as a yearly cycle. The structural ramifications of this concept are staggering. When we consider that the yearly cycle contains 58 works at, let's say an average of twenty minutes each, we are dealing with Ring of the Niebelungen scale. The striking way that this aria begins with no orchestral introduction, interrupting a recitative of a different voice, affirms that Bach knew that this was a bold and dramatic gesture. It could not have escaped Bach's notice that this trial by water was somehow related to the previous week's trial by fire. The four-voice harmonization of the chorale that ends the cantata is so characteristic and yet so powerful that we cannot fail to marvel at the endless inventiveness of these harmonizations.