I have a friend who can't carry a tune in a bucket, but loves to sing. What he does is fascinating. Every time he misses the correct pitch, he resets to that key. Two notes later he misses again and the key shifts once more.
Is that common, do you suppose?

And this other thing, about myself. I love to sing harmony, and sometimes I am right on, sometimes not. What I have learned about myself over the years is that if I can hear the note I am singing internally, I am on pitch. If I can't hear it, I'm off. Anyone else have that experience?
Blessings,
Barbara