Although it is sometimes placed in the 3rd Jahrgang, the Cantata BWV 129 is much more characteristic of Bach’s Chorale Cantatas of the 1730’s. Although in the five verses there are references to the Trinity and the piece is usually listed as being written for Trinity Sunday, there is none of the specificity that we saw in the 1st two Jahrgangs. The chorale is a text written in 1665 and performed to the tune “O Gott du Frommer Gott.” Although it is a work of great detail and real resource, there is something very ungainly about it. Each movement has tremendous difficulties for the performers. We are used to Bach setting very high standards for his musicians, but the cello part in the 2nd verse and the flute and violin parts in the 3rd verse are unusually virtuosic. In fact one sees the influence of the kind of French virtuoso flute and violin writing found in works like the Telemann “Paris” Quartets recently published and no doubt known by Bach. Of a more mysterious nature is the long and exhausting oboe d’amore solo in the 4th verse. The opening chorus movement with trumpets and tympani also has a long note chorale in the sopranos pitched unusually low with no instrumental doubling. It is virtually inaudible unless a doubling instrument is added. All of these issues add up to the fact that, like the other eight purely chorale cantatas, there is something peculiar and impractical about them.
Despite all of this, our cantata is a vivid and energetic piece. The opening chorus has a wonderful motoric theme in the strings and winds with marvelous brass punctuation. After all of the wonderful stepwise energy there is a passage of real extravagance and imagination that keeps reappearing throughout the movement. Unlike many of the 2nd Jahrgang choral fantasias, the chorale tune is not spread out but appears in half notes in the soprano. This emphasizes that effect of this being an instrumentally dominated movement
The 2nd Verse a bass aria with continuo is like all of the movements except the fourth, very lively. It really needs to go at least ? = eighth. The whiplash 32nds at the top of the big leaps are really bracing. For all of its speed, there is an elegant and ornamental quality to the opening ritornello. All of the middle verses divide the six lines of text into two three- line groups of about equal length. Although this aria begins with an ornamented version of the chorale tune, it soon deviates from it significantly. All three middle verses however preserve something of the harmonic shape of the chorale.
The Soprano Aria, Verse 3 also moves at a real clip. It is dominated by a glassy scale figure in both the obbligati and the continuo. The voice part pursues the opening theme independent of the scale figures. This theme acts rather like a chorale but is completely independent of the chorale theme. It is curious that this new melody is pursued also in the next aria. Again, the six lines are divided into two groups of three, preserving the basic harmonic outline of the original chorale melody.
All of the ritornelli in the Alto aria #4 with Oboe d’amore obbligato are very long; the first one lasts full 24 bars. Although by this time our chorale has virtually disappeared as a melodic element, there is a sense that its six phrases are represented in each of these ritornelli. The only melodic relationship is that the melody lands on the sixth degree of the scale, just like the first phrase of the chorale. The aria is so blandly pretty in such a generalized way that the striking gesture of all voices going to a unison at the mention of the Trinity comes as something of a shock. We are used to this kind of extreme text painting in much more specific music.
The final chorus is more pompous and ceremonial than the first but much the same in scoring and effect. This is an ideal cantata for concert performance because it is so brilliant and it makes no elaborate theological demands on the audience. For those interested in the serious side of Bach it will be something of a disappointment.