I am only experienced with Phonak and have their Target software to program my aids, but from what I have been reading most of the other hearing aid manufacturers have similar functionality.
To improve hearing voices, there is a default setting that shifts the sounds down to a frequency that the majority of people will be able to understand without making drastic changes to the default programs. In my case, I do my own programming, and have setup a dedicated music program that I use when playing my Classical Guitar or mandolin. It’s almost analog and has everything turned off except the basic settings I needed to compansate for my hearing loss. Whenever I want to play one of my instruments, I select this program, and the music is in perfect tune and sounds great.
You will need to have your Audiologist make the changes for you, assuming he understands your needs, and has the skills to do this. From what I have read, most audiologists don’t have a clue when it comes to working with musicians. You may need to shop around for someone, or do as I and many others have done, aquire the programming software, and learn to DIY.
If you do stick with an audiologist, make sure you can bring your instrument with you to validate any changes he makes,
When you do your own programming, you can make changes on the fly, without an appointment. It’s very liberating.
Good luck.