I've been a professional musician for more than 40 years. I can hear quite well, can whistle in tune, and can't carry a tune in a bucket with my voice. I've worked with multiple voice teachers and many very good vocalists in bands. My ex-wife, who used to work with people with brain injuries, thinks it might be brain damage from falling on my had a couple of times when I was young. Apparently, loss of a narrow band of functionality is fairly common with brain injuries, like people whose only problem is they can't taste salt or something.

I know how to provide good support, how to relax my body and throat, and I can hear exactly what I want to sing. Something else almost always comes out.