BWV 653a is a variation of Bach's famous "An Wasserflüssen Babylon" chorale prelude, offering a slightly different perspective on the same profound musical material. It continues to be a significant work for its contrapuntal mastery and expressive depth.
Mastering the intricate fugal development and controlling the vast dynamic and textural range are the principal technical hurdles.
An Wasserflüssen Babylon (BWV 653a) is rated Henle level 7 of 9 — late advanced repertoire, roughly ABRSM grade 8 and above. In the RCM system it corresponds to about level 10.
You should be comfortable at Henle level 7 — meaning you can already play level 6–7 pieces cleanly. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
A typical performance of An Wasserflüssen Babylon (BWV 653a) lasts about 6 minutes.
An Wasserflüssen Babylon (BWV 653a) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.