Free through-composed fantasia, beginning with an imitative entry. (= theme 1) for the first 10 bars. There are, thereafter several superficial attempts to give cohesion, and whilst successful don’t help to create a more significant work. In particular the rhythm M Sm f f | M is used towards the end as a rhythmic imitation, in the same way that |M. Sm|M occurs in theme 1 (as does the former motive). The use of Bb throughout much of the work makes it sound to me more like mode 2. Theme 1 is perhaps mode 8 (7 too!).