Anyone else find music with SSHL off key?

I also like classical music and have many music tapes that I recorded years ago. Recently they sounded strange -- choruses going flat! I think it might be old tapes or the tape player. Hope it's that. Music seems to be OK on TV and my computer.

I have a friend with a hearing problem the doctors can’t help her with.

When she sings, she hears the notes both on key, and off key (sour) at the same time.
She is a professional singer!
The top doctor hasn’t been able to help, and she has had shots and other things.

She applied to Mayo, but they wouldn’t see her…

As I get older my hearing is getting worse, no surprise there. I have had tinnitus for years as a background sound and that is now part of my hearing deficit.
When I walk or bike alone, I use my light-weight, $15 headphones (like Sony MDR-ZX110) and my MP3 player to listen to music.
The sound is clear and wonderful! I can hear from bass up through the midrange with no problem.
Because I am an electronic engineer I keep wondering why someone does not make a small device that has a full range microphone on each ear of a set of headphones with an adjustable 5 or 6 frequency band filter so that one can adjust the volume in each band until it sounds "right" for each persons individual hearing loss. This would make a great "hearing aid". Anyone know of such a device? It could be made quite inexpensivly. I know you would look kind of geeky holding a conversation with headphones on but in this age of electronics it is commonly seen when interviewing people on TV.

@crossette, since you're an electrical engineer. and you know what your talking about and you know what you want. why don't you build them yourself? just find a computer designer to help you out. simple? (NO). (YES). (MAYBE). 🤷‍♂️🤷‍♂️.

I wanted to ask some people to see if they knew if someone is making such a thing first. No sense in repeating the work if something like this is already out there somewhere. I am a little busy on other projects right now too.