Bach's Chorales are harmonizations of Lutheran hymns, showcasing his masterful command of voice leading and harmonic progression. These pieces are essential for understanding fundamental tonal harmony and contrapuntal texture.
Focus on the independence of each melodic line and the smooth flow of harmony.
383 Chorales, D-B Am.B 46/II is rated Henle level 1 of 9 — beginner repertoire, roughly ABRSM grades 1–2. In the RCM system it corresponds to about level 2.
You should be comfortable at Henle level 1. Learning it one level early is possible as a stretch piece, but more than that usually leads to months of frustration.
383 Chorales, D-B Am.B 46/II is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.