I had a student come into her lesson sounding much much better than she had the week earlier. Her Mozart Concerto was stylish and flowing, her intonation was excellent, and she had a focus to her sound that was new, and welcome. What had she done in her practicing to make such a difference?
I recorded myself, she announced, just like you suggested!
And my mind was blown. I suggest that a lot, but I've never had anyone really do it and improve themselves that much. The idea often seems to go in one ear and out the other, like Practice with your metronome and Don't use that Eb key on your forked F.
I do recommend recording yourself. It is one of the many tools you can use to improve your own playing, and to be your own teacher. It can be difficult, though, to do it well and get good information from it.
I record myself often, but if I'm not really focusing on the goal at hand I can listen back to what I've just laid down, say Yup, that was Mozart, all right, and move on. It's very hard to get critical distance from the work I've just done. By the time I am ready to record myself, I have played the piece over and over and settled on the way I want it to go. I'm used to the way I sound playing it. I'm used to the nuances I take, used to the intonation of my instrument, comfortable with the way I'm feeling the pulse and rhythm. And since I've not had a teacher in years there is no one to tell me No, that choice is a poor one. Don't you hear how sharp that B is on your oboe? That attack was awkward.
So I have to take a step away. I record, I leave the room and come back, and I pretend. Ooh, I say, sometimes out loud, I have a new recording to listen to! It's a colleague who has asked for some feedback on her playing. She's taking an audition soon and really wants some ideas to work on.
And now, as soon as I start the playback, I hear faulty intonation. I hear clunky trills. I hear sound quality that comes unglued, or vibrato that spreads too wide or becomes meaningless. And whatever stands out to me the most is what I work on for the next hour. I re-record. I re-pretend. And eventually I can make some real headway in improving even a piece that I know like the back of my hand, that I've been performing for years, that was already pretty good.
The recording equipment itself doesn't need to be spectacular - I use Garage Band on my Mac, or sometimes Photo Booth if I want visuals. It's just for me, after all. And it's one of the hardest and best things I do for my own playing. My student's recent success has reminded me that it's good for more people than just myself.
Have fun, and happy listening!