I agree with the misdiagnosis bit - I was certainly incapable of producing (or hearing parts of) pitch till I got away from my incredibly tone-deaf models at home and got into a musical dorm in college. But I could always tell THAT two tones were different, even if I couldn't reproduce the difference or say how large the difference was. My mom, however, not only can't tell whether 2 tones are the same or not, given 2 tones that ARE different she can't tell which is higher. And HER mother was very musical so it wasn't a modeling thing, she and one of my sisters really are terrifically tone-deaf. And one of THAT sister's daughters has perfect pitch, go figure. So there IS something to tone-deafness, even if there are also misdiagnoses, I think.