It's a little bit strange, but harmonically holds together quite well with the use of canon. That part's great! I wasn't a fan of your Klangfarbenmelodie sometimes though, especially when it introduced syncopated rhythms since one normally continued without the other. Other than that, it's a fine miniature.
The prelude definitely have some Hovhaness vibe to it. Nice buid-up to the fugue. Interesting fugue, as well. Doesn't seem like a fugue in the strictest sense, but then again, there are those that defy common compositional practices for fugues, so yeah, good work!
Interesting. The use of old themes is pretty clear, as it definitely sounds pretty segmented. I really do enjoy the themes, but it just doesn't feel very connected, both in character and in flow. And especially in the begging you go at what feels like a mile at a minute in changing the theme and character before the the a rehearsal letter D which you do a better job of developing. The piece overall feels like you could build it into several movements of a piece and it would work quite well.