What do you mean by "improve the sound and expressiveness" and make "more pleasant for your ears"?

You processed some recordings you found of these pieces, I guess? What were the original inputs?

Just listening to the first one, Op. 9 No. 2, it sounds "ok", like it's been processed through a compressor with some Reverb, maybe? I think it's lacking dynamics and expressiveness compared to other performances out there.

Yundi Li, for example