I've spent about eleven years of my life in various choirs, and I am still effectively music illiterate. I'm capable of singing perfectly well, but the terms "flat, rising and falling tones" mean nothing to me. I can't read sheet music, remember the names of notes, I'm not even sure I remember what a scale is...

It's not that I haven't tried to learn these things, but for some reason I've found myself completely unable to retain any of it, despite having plenty of opportunity to make use of the information. I can only speculate on what the reasons for this might be.