BWV 173a

Durchlauchtster Leopold (Most illustrious Leopold),BWV 173a, is a secular cantata by Johann Sebastian Bach. Bach composed the cantata in Köthen for the birthday of Leopold von Anhalt-Köthen.

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 relatively simple work may have been written in some haste already in 1717, when Bach had been appointed Kapellmeister, according to Alfred Dürr. However, this is not likely, because Bach was still in the process of moving to Köthen on 10 December 1717 (having been released from his imprisonment in Weimar on 2 December 1717). The libretto even shows a date of "before 22 December 1722". So, in all probability, the work and first performance of it date from 10 December 1722.

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 "Durchlauchtster Leopold", 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 Die Zeit, die Tag und Jahre macht, BWV 134a, but are not marked in the text.

In 1724 Bach used six of the eight movements to form his cantata for Pentecost Monday Erhöhtes Fleisch und Blut, BWV 173, and in 1725 he took movement 7 for his cantata for Pentecost Tuesday Er rufet seinen Schafen mit Namen, BWV 175.

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