This aria, BWV 508, is one of Bach's most beloved and frequently performed pieces, though it is actually by Stölzel. Its beauty lies in its profound simplicity and heartfelt expression of longing and devotion.
Focus on a lyrical, singing tone and a careful shaping of phrases to emphasize the emotional depth.
Bist du bei mir (BWV 508) is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 3.
You should be comfortable at Henle level 3 — meaning you can already play level 2–3 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 Bist du bei mir (BWV 508) lasts about 2 minutes.
Bist du bei mir (BWV 508) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.