My Dad would have been with you on that one
very strange Liverpool accent
My Dad reckoned she started out with a real one - was persuaded by London executives to loose it
Then the Beatles happened and it was suddenly cool to have one so she re-learned it
but it never really worked
never heard anyone from the whole area that sounds anything like her - just weird!
Oh - and on topic - any operatic soprano
can;t stand the whole tone they use
ESPECIALLY that warbley thing - goes right through me
I did hear one once that was brilliant - no-idea who it was but it was someone famous and seemed to manage to do it without warbling annoyingly and with a more natural tone