The 17 "Leipzig" chorale preludes of J.S. Bach are called thus not because they were composed in the city of Bach's cantorship, but rather because it was in Leipzig that Bach, sometime during the last few years of his life, revised them and put them together as a single volume of music. Most of the preludes of the group were actually crafted 30 or perhaps even 40 years earlier, during Bach's years in Weimar. An exception to this is the chorale prelude on An Wasserflüssen Babylon, BWV 653, which seems to be one of just a handful of organ works written after Bach had moved on to Cöthen and, for the most part, from sacred to chamber music.
In BWV 653, Bach embeds Wolfgang Dachstein's 1525 melody An Wasserflüssen Babylon in richly ornamented counterpoint. The chorale melody, or cantus firmus, is itself highly decorated, and is placed in the tenor voice; its many phrases -- the first long (and repeated verbatim), the rest no more than four bars each -- are isolated from one another by passages of varying lengths for just the other voices. Only the bass line is without intricate ornamentation -- understandable, as, thanks largely to the innovations of Dutch chorale prelude pioneer Jan Pieterszoon Sweelinck, it is played on the pedals. BWV 653 is a work that Sweelinck, or Pachelbel, or Buxtehude (all masters of the chorale prelude) would likely embrace: like most of the "Leipzig" chorale preludes, the piece reaches back into the vault of Germanic organ tradition. Even -- perhaps especially -- during his final years, Bach's debt to the composers of his youth was in the front of his mind. There are two alternate versions of the prelude on An Wasserflüssen Babylon; they are known as BWV 653a and BWV 653b.