A few days ago I published the score of one of the compositions of which Bach's authorship is doubtful, namely the choral prelude "Wer nur den lieben Gott lässt walten" (BWV Anh. II 68). That composition shares the introduction and the ending with another of the doubtfull works, the choral prelude "Helft mir Gottes Güte preisen" (BWV Anh. II 54). That made me wonder whether I could find a suitable choral melody to create a third composition using the same material in a way that seems to be specifically written for that choral melody.
A suitable candidate is the melody of the choral "Auf meinen lieben Gott". The melody of "Helft mir Gottes Güte preisen" starts with the notes f sharp, b c sharp, d and e.
The melody of "Auf meinen lieben Gott" starts starts with the notes b, b c sharp, d and e.
It is just a small step to pretend the first note of "Auf meinen lieben Gott" is an f sharp as well, instead of a b. I chose to use the introduction of BWV Anh. II 54 rather then the one of BWV Anh. II 68 because I think the latter contains some superfluous additions and the first one seems to be the original of the two. Everything bwtween the introduction and the ending of the piece is music of my own invention. I modelled my music on both other compositions with respect to where to place shorter and longer fragements between phrases of the choral melody. The result is hopefully a composition that could have been written by someone in the same circle as where both BWV Anh. II 65 and BWV Anh. II 68 originated.
The recording was done with the Hauptwerk software and the sampleset, made by Sonus Paradisi, of the Schnittger organ in the St. Martini-kerk, Groningen (https://www.sonusparadisi.cz/en/organs/netherlands/groningen-st-martini.html).
Score available here: http://partitura.org/index.php/auke-jongbloed-auf-meinen-lieben-gott