a related question asks if there is a specific term for the voicing in Bach's Chorals:
I would have said this is the Choral.
But what I am wondering is how we name the instrumental accompaniment of the solo violin in Jesu Joy or the Bassoon Solo in BWV 140 Zion hört die Wächter singen?
I think we could call it: Ornament, Garland or Ritornell.
Other ideas?
(As I'm planning an analysis and introduction "how to learn and teach" this arrangement/setting for piano).
In the cantata form as used by JS Bach, these "chorale fantasias" often have an elaborate orchestral introduction. The opening of BWV 244 (the St Matthew Passion) has often been described as such, and both the opening movement and the final movement of BWV 147 Herz und Mund und Tat und Leben fit this pattern.
However, the structure of the chorale fantasia conforms fairly well to a sort of ritornello form, and hence as the opening theme of the movement does return and punctuate the chorale setting itself, to call this theme a ritornello is appropriate.
