This chorale prelude is a more introspective setting of the hymn tune. Bach focuses on a lyrical unfolding of the melody with delicate ornamentation.
Cultivating a beautiful legato touch and nuanced phrasing are essential for conveying the piece's tender character.
Allein Gott in der Höh sei Ehr (BWV 717) is rated Henle level 3 of 9 — late beginner repertoire, roughly ABRSM grades 4–5. In the RCM system it corresponds to about level 4.
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 Allein Gott in der Höh sei Ehr (BWV 717) lasts about 2 minutes.
Allein Gott in der Höh sei Ehr (BWV 717) is available as free public-domain sheet music on IMSLP — the score is linked directly from this page.