Listening to music at low volumes does nothing to improve your hearing. Otherwise, the method would be used in the treatment of hearing loss. Presumably, listening to studio quality music with good equipment can positively affect the perception of sounds, the ability to distinguish frequencies, tones, provided that hearing is healthy.
Like any other disease, it is easier to prevent than to cure. If possible, discard in-ear headphones, as they do the most harm (a little deaf, using the CX 5.00G). Using headphones, you can achieve the proper volume level at lower dB values, as the auricle is a natural sound amplifier. Also, in noisy environments, do not try to isolate the sound completely by only increasing the volume. Adjust the volume so that you can hear the voices of people sitting next to you.
The best way is to enjoy good music at home in a quiet environment.
Listen at high volume - eardrums deteriorate. They lose their elasticity both over the years and with such loads. If you listen quietly, your hearing is unlikely to get better. In this case, in semi-deaf people it would constantly improve :)
But I would like to note separately that it is possible to improve the quality of PERCEPTION of music - it is quite possible. It takes a month or more to walk around and listen to high-quality expensive headphones. More than once I saw how people who were not picky about the sound quality at all (because they did not perceive the difference) began to understand over time what was the point :) Examples of more or less good headphones: 1. Sennheiser CX-300-II, CX-500 2. Sennheiser HD-380-pro. These are all home headphones that actually sound pretty good.
I don’t know the theoretical basis, but my hearing (after I have been using headphones at low volume for several years) is not much sharper, but more selective, or something. In the sense that it became easier for me to isolate and make out some quiet sound in the general sound background.