Composed for Quinquagesima Sunday, the Sunday before Ash Wednesday and therefore the Sunday before the start of Lent (which fell on February 7, 1723), Bach's Cantata No. 23 "Du wahrer Gott und Davids Sohn" (You true God and David's Son) (BWV 23) was composed along with Cantata No. 22 as part of his application for the post of Thomaskantor in Leipzig. The cantata's first three movements were composed in Cothen for trial in Leipzig while the fourth and final movement was added after Bach had gotten the job in Leipzig, and the entire four movement cantata was first performed in 1724. Although it paraphrases Psalms 15 and 145 and its final chorale is a setting of the Agnus Dei in German, the text seems not to have been based on any pre-existing Lutheran hymn and its author is wholly unknown. The cantata is scored for soprano, alto, tenor and bass soloists, chorus, pairs of oboes, strings, and basso continuo. It's in gloomy C minor with its first and fourth movement in the tonic and its second movement starts in the tonic, but it closes in the relative major of E flat with the third movement entirely in the relative major of E flat. The Adagio molto first movement starts with an imitative duet for oboes, followed by an extended canonic duet for soprano and alto soloists. The second movement is an a tempo recitiative for tenor, oboes, strings, and basso continuo. The third movement and the original ending of the cantata is an enormous rondo-form movement for chorus, oboes, strings, and continuo with tenor and bass soloists. After a dancing instrumental opening, the chorus alternates with the soloists for the remainder of the movement. In its final version, "Du wahrer Gott und Davids Sohn" concludes with a setting of the Agnus Dei for chorus and full orchestra that begins as a mournful Adagio and closes with a slightly more hopeful Andante. ~ James Leonard, All Music Guide
