When I was a student, I had small hand held cassette players with unstable pitch fidelity for recording ourselves. After awhile, I got used the the variables and could still discern relevant information while praying that I didn’t actually sound like that!
Then I got a Yamaha dual deck variable pitch cassette player for recording myself. It was good because I could run it with my toes… the controls were big tabs like plastic piano keys. The variable pitch would allow for slowing down the playback. It also allowed me to play along with recordings of higher pitched European orchestras.
Then I had a Nagra reel to reel which would play back at half and quarter speed — best thing ever. I could play my fastest excerpts then slow the playback to quarter speed to analyze the gaps in my technique.
(I sold this fantastic machine to pay for my first baroque bassoon. I sold that bassoon to pay for a recording project.)
Now I just got myself a Zoom video recorder; I have never ever used a video device for practising!
Whatever you use, it will help. Better than a teacher, it multiplies the practise benefits enormously. Record yourself. Then make a recording.