Nick, perhaps I should have said I've rarely found it a problem moving a semitone for a song. I hardly ever sing now and can struggle when I do but when I was singing fairly regularly, I think "Freeborn Man" was one of the few I sometimes did where I had to be quite careful where I started (make sure I could sing "lumbered" at the low end and pitch it from there).

I've never felt a singing key "right" or "wrong" as long as it's in comfortable range which for me always seemed to vary a bit... Any ideas why it should be for some? Perfect pitch?