Try this one. About as classically trained as you can get:

Ruhi Su

Does it sound like somebody who'd had a career singing Western opera?

The song in that clip is a lament for the leadership of the Turkish Communist Party, murdered on Ataturk's orders in 1921. Ruhi Su was the leading classical opera singer in Turkey, sacked for his politics. So he went into folk music and became something like a combination of Woody Guthrie, Leonard Cohen and Bert Lloyd, while reaching greater general recognition than any of them did - a bardic figure who communicated to an entire country for a couple of generations.

There's a Wikipedia page in English that gives more detail. Lots more clips on YouTube and other websites.

One of the best performances I've ever heard of a Scottish song was by Rita Streich. The really big thing she'd learned as an opera singer was how to be witty and touching at the same time. She had a slight Austrian accent but so what - all the feelings were in the right place and her timing was spot-on to the millisecond.