Martin Luther's chorale version of Psalm 12 is the sole source for Cantata BWV 2. While the unnamed author of the text has arranged the various verses into chorus, recitative, and aria format, the sense and character of the Luther chorale remains unusually pure. It is characteristic of Bach when dealing with Luther that the ideas remain more or less unadulterated.Bach treats the opening verse of the chorale in an archaic neo-Renaissance manner. A strict four-voice texture with independent continuo line is observed throughout. Of the five chorale-based choruses in this style, four are to Luther texts. It is clear that Bach associates this manner with bedrock Lutheran theology. By having the chorale in the alto voice rather than the usual soprano, Bach submerges the sinner in the texture, looked down upon from heaven by the sopranos. The harmony is of the densest sort. Phrygian melodies are among the most difficult to convert to tonality, but here Bach jumps into crabbed and ambiguous harmony from the outset. It must be a manner that he associates with this tune, for the organ setting in the Kirnberger collection is similar in density and unique in that collection for its harmonic daring.It is interesting that the phrase structure remains quite clear and one could almost say simple. When we think of the elaborate phrase overlaps in the treatment of the previous week's chorale tune, O Ewigkeit, du Donnerwort, these phrases seem very direct. One senses that the very complexity of harmony is enough for Bach here. Also there is an extraordinary economy of motive. The subject, derived from the tune and two counter-subjects, contains virtually all of the material in the movement. The doubling by the trombones emphasizes the archaic nature of the music.A line of the chorale sung by the solo tenor with continuo sets off the following recitative. While this seems at first to be in Bach's familiar manner of chorale with tropes, no further musical reference to the tune occurs, so we must assume that Bach feels the need to make a transition to the more modern recitative style. The elegant alto aria with solo violin is in striking contrast to the severity of what has come before. Clearly the chattering violin part is meant to represent the Rottengeistern and the Ketzerei. There is a marvelous moment when the suave continuity comes to a stuttering halt at the words Trotz dem. A fragment of the chorale tune enters like a beacon bringing us back to the seriousness of the subject.
After the harshness of the harmony in the opening chorus and the elegance of the alto aria, Bach finds yet another color for the bass recitative. Here is a marvelous example of the variety to Bach's chromaticism, harsh dissonance and vertiginous progressions in the first chorus, melting and soft edged progressions for this recitative. The first two bars of recitative show how carefully Bach gauges his harmonic color. Notice the darkness at the word verstört; the stab of pain at the word Ach. This is not only a change from the brittle Bb major of the alto aria, but a transition to the radiance of the “alchemy” aria #5.In a work such as this cantata one can be so amazed by the harmonic detail and astonished by the contrapuntal deftness, that the sheer melodic invention can be forgotten. Certainly a tune such as in the aria Durchs Feuer wird das Silber rein reminds one that the lessons learned by Bach in his transcription of Italian concerti were as important as his German contrapuntal heritage. The principal melody is worth looking at in some detail: notice how the eighth and two sixteenth note figure is turned upside down in bars 2-3. The beginning sequence of bars 2-3 is itself turned upside down in the 4th bar. This is yet another example of subtle changes in what could be a garden-variety sequence to create a varied and highly profiled melody. It is one of those tunes that once heard is never forgotten. Clearly, Bach found the metaphor of the refining of the silver as central to the message of the cantata.
The final chorale, while still very chromatic, has somehow lost the harsh language of the opening chorus. Bach never leaves the listener unchanged by his musical experience.