Meryl Streep is brilliant with accents. She must have a good ear for them. Dick Van Dyke's attempts at Cockney were hilarious, poor chap. He spoke/sang in 'Van-Dykese' in my view.

It isn't easy though to sing a song and put on an accent simultaneously. I used to sing 'Delaney's Donkey' and 'Paddy McGinty's Goat' to my class, and in spite of having an Irish mother, I expect my attempts were woeful!