Durchlauchtster Leopold, BWV 173a
History and words. Bach composed the cantata as a congratulatory cantata, also termed serenata, for the 28th birthday of his employer, Leopold von Anhalt-Köthen, on 10 December 1722. The holograph manuscript survives in Berlin, but cannot be dated exactly. The libretto shows a date of "before 22 December 1722". Bach may have begun the work when he was appointed Prince Leopold's "" in 1717, according to Alfred Dürr. If this hypothesis is correct, Bach would potentially have had a few months to compose a work for the prince's birthday, but even relatively simple  music could have required some haste given the circumstances in which he left his job in Weimar, being imprisoned by his employer for not following correct resignation procedures. Bach was released on 2 December and was still in the process of moving to Köthen on 10 December 1717. The unknown poet wrote eight movements. Only two of them, 1 and 5, are recitatives, but even these are regular in meter and rhyme and may have been intended for arias. The first recitative even shows a da capo of the first line, addressing "", translated to "Most illustrious Leopold" or, more literally , "Most Serene Leopold". The two vocal parts may have been allegorical figures, as for example in the cantata for New Year's Day , but are not marked in the text. In 1724 Bach used six of the eight movements to form his cantata , for Pentecost Monday, and in 1725 he took movement 7 for his cantata for Pentecost Tuesday . Publication. The cantata was published in 1887 in the first complete edition of the composer's works, the Bach-Gesellschaft-Ausgabe. Scoring and structure. The cantata is scored for two vocal soloists (soprano and bass), two flauto traverso, bassoon, two violins , viola and basso continuo including violone and harpsichord. The last movement is marked chorus, but was probably performed by the two soloists. Music. Bach composed varied music for the rather monotonous text. Movement 1 is accompanied by the strings and leads to a virtuoso coloratura on the da capo of the first line, addressing Leopold. Movement 2 is reminiscent of a dance, gently scored for flutes and strings, in triplets. Movement 3 is a short praise movement, marked vivace. Movement 4 is a duet, marked "Al tempo di minuetto", which handles three stanzas in ever richer variations: the first stanza  is for one voice and strings in G major, the second in the higher key of D major with additional flutes, the final one for both voices in A major in a denser musical texture. The structure of this duet is unique in Bach's cantatas, the variations in rising keys, and the increase in instruments and musical texture all adding up to illustrate the exaltation of the addressee. Movement 5 leads to an arioso. Movement 6 is a bourrée, dominated by a flute which comes and goes. Movement 7 is in great contrast set for only low voice and  instruments, bassoon and cello in unison to a continuo played by violone and harpsichord. The final dance-like movement shows elements of a polonaise. Its two parts begin both with an instrumental concerto which is then repeated with embedded voices.