This chorale prelude by J.S. Bach, part of the Neumeister Collection, is a thoughtful exploration of a penitential chorale. Its musical distinctiveness lies in its dignified melody, subtle harmonic richness, and contrapuntal interplay.
Requires a clear sense of the melody against the contrapuntal lines and a sober, expressive tone.
Ach, was soll ich Sünder machen (BWV 259) is rated Henle level 5 of 9 — late intermediate repertoire, roughly ABRSM grades 6–7. In the RCM system it corresponds to about level 6.
You should be comfortable at Henle level 5 — meaning you can already play level 4–5 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 Ach, was soll ich Sünder machen (BWV 259) lasts about 3 minutes.
Ach, was soll ich Sünder machen (BWV 259) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.