Even though yo urecorded it just for fun, I have to say I found it not as satisfying as your others even the Scriabin (which you apparently also did for "fun", and it was that one that made me go listen to your others!)I think the piano approach should be different in the music of Medtner, not be so Scarlatti-ish, but a bit heavier with arm weight, and a more pronounced cantabile. But I mean something rather specific, and that is, more extroverted cantabile that is operatic in style, not Lieder in style. Also I think the tempo is just too fast. Your time is about 8 minutes but most people seem to take 10 or 11? Especially since a lot of the figurations come from the opening page, if they are too fast they are blurred and the motivic reference is lost.It matches your other offerings for brilliant technique and charismatic excitement. Don't worry that it is not "finished," because it is so much more exciting than many others finished products.The Earl Wild recording also doesn't have a finished sheen to it, if I remember correctly. I've never heard the Hamelin of this sonata.Walter Ramsey
Your performance is quite impressive, and you certainly do have a good technical command of the keyboard. Medtner thought of himself as a pupil of Beethoven in spirit, and that is evident in how he develops his thematic material. What I find intriguing is that there is very little fluff in his works, every motif has meaning both thematic and accompaniment - especially in this sonata. Yet the music still manages to be very pianistic and romantic in nature. There are many dimensions of line in this piece, a lot of the time multiple instances of line are superimposed on each other. I think you need to bring out this contrapuntal facet of the music much more. Rather than thinking of vertical exactness, you would do good to search out the beginnings, climaxes and endings of line in this piece.
This pieces also has a wide diversity of character, like instruments of an orchestra. I'd like to hear more of a pronounced contrast in character. You have much more room to be poetic in the slow sections, while you can do more to additionally emphasize the percussive effects of the opeining theme and it's transformations. Also further tuning yourself in to the dialog between thematic elements would help you fine tune your pedalling to emphasize certain elemenets, so that they can more clearly emerge from the mass of notes one needs to play.
I'd also like to hear more varying nuance in your quiet sections. Make full use of the una corda and fractional una corda pedaling. It's great to hear some Medtner on here!