I lost my hearing (a 3db rolloff) above 6k in my right ear when I was about 60. But my left ear stayed reasonable full range, and I found the brain compensated nicely the the missing frequencies, and especially kept phase relationships intact. This was caused by a case of Bell's Palsy that paralyzed about all the muscles on the right side of my head (eyes, mouths, cheeks, etc. ... and apparently the ear as well.)
But in the last two years I've lost the hearing in my left ear .... classic old age rolloff. Suddenly everything vocal is mush, and music ambience is virtually non-exitence. The only way I can really enjoy music (stereo or live) is to cup my ears and boost the upper midrange in the process. Tomorrow I am going to pick up some decent hearing aids, and this will help my conversational hearing. I'm not so sure I'm not going to prefer "cupped ears" to the aid when it comes to music.