[gbajson]

What do you think about applications like Simply Piano? I am 40+ yo, and never played any instrument before. After 3 years of practicing with Simply Piano I am able to read and play some sheet music, but I'd like to know which areas need improvements.

Do you know any applications which can record performance of a song and evaluate it?

[djaychela]

I don't think this is a solved problem yet, in terms of technique. You may well be pressing the keys in the right order, at the right time, and with the right dynamics, but there's a lot to playing technique that is about your hand position and movement which isn't detectable via MIDI capture.

I've been a guitar teacher for 20 years, and I've seen people who are incredible players with terrible technique. Yes, that means it's possible to play well by doing so badly, but with the right technique (which is still being developed in some areas), there's a whole lot of improvement that could happen, or the player in question could play for longer (both in the short term, and longer term because of injury).

Only complex video / 3D capture of your hand position and movement would solve this, and as far as I'm aware this doesn't exist yet.

Find a good teacher, even if it's just for the occasional lesson. With the right teacher (and this is horses for courses), you'll make much more progress, even if you still use the app.

(All IMO, of course!)