With a life-long interest in Scottish ballads, I've had an ongoing concern about accent when singing. It's my preference to hear the old traditional texts sung in what has been described as 'ballad English' -- which I take to mean a text with fewer Scottish dialect words than other non-ballads, but with Scottish vowel sounds.

I'm imagining that it's the vowel sounds that push things awry, so that people then complain about an American accent when listening to more recent compositions. And there is an associated (big) question about why performers should imagine that this is either preferable or necessary.

Personally, I prefer to hear a singer who enunciates clearly (not in a clipped, precise way) and who delivers a song with an understanding of the story.