"accents and word usage of the semi-literate white people"

Well, I think it's hard for white, middle-class singers to sound like Appalachian singers. If you're from another culture, I think it's wise to put no more than a hint of another accent into your singing. If you put too much, you'll sound like a caricature.

As for Wagner, I do think that if you sing in a foreign language, your pronunciation should be credible (even if some nuances aren't perfect). If you're going to sing "Edelweiss," don't go pronouncing it "Idlewise."

Maybe it's wise to note the difference between accent and pronunciation - pronunciation should be correct, but accent may be another matter.

-Joe-