Hi faj,
You play this impromptu with confidence and care, producing much beauty. The melody is voiced well in the right hand and always shines through, and you draw a very nice tone from the piano. The 4th and 5th fingers carry most responsibility for connecting the legato melody. To attain that singing legato, some pianists like to sing the melody in their minds as they play. I was intrigued by birba's excellent suggestion on reducing tension while etching the melody. You have a nice evenness in the filigree accompaniment within the right hand and keep it unobstrusive. Your pedaling is judicious throughout. Very nice.
As for dynamics, most of this work is marked pp and is even ppp at times. (For ppp try leaning backward on the bench until your forearms feel as though they are floating on air with your hands over the notes. It should, along with soft pedal creating a different timbre, help to attain that extra level of quietness. Schubert allows a bit of Fz in bass harmonies now and then, and there are a couple of short moments at f until the last page where there are a couple of ffz. Yet for the most part this is a very quiet, tranquil piece. That raises the difficulty of adding color. So you'll need to exhaust every dynamic change Schubert allows. Of great importance is executing the many < cresc. decresc.> notations. Those breathe more life into the music too. The different timbre of the soft pedal can also provide variety of color as already mentioned.
This is one of those pieces where the pianist layers the sound, which you attend to well. The RH melody, of course, takes first priority in the foreground. The resonant bass harmonies, although accompaniment, are more important in my opinion than the filigree accompaniment in the RH which is last priority. But those bass harmonies still cannot compete with the melody in volume, as they are background, yet important harmonic changes need to be apparent. There are moments too when the bass harmonies contribute scalar passages (measures 19, 51-52, 58, 65, 79-80 as examples). Scales are extremely important in musical understanding, so these always need to be made apparent to the listener. They don't call for exaggerated emphasis, but enough to make their presence known.
Finally, I agree with cbreemer. If your room acoustics will not permit the piano lid to be fully raised, could you perhaps raise it on the shorter lid prop for a serene piece such as this one? It would allow more of the sound to escape the piano case giving the music an even richer sound.
Again, faj, wonderful playing!
David
Topic: [Video] Schubert Impromptu Op. 90 No. 3