Thanks russ, interesting answer - but *grin* that wasn't the question I was asking. or at least it wasn't the question I thought I was asking.

Perhaps I wasn't asking it correctly - I wasn't asking about the validity of a variation - but rather what standards someone would use to accept it as a variant - rather then just a "personal twist" or "learned wrong"

and I'm curious. if a brooklyn neighborhood has a consistant set variation of a tune or song - what makes that less valid then one learned in Pocahontas County WV?