I think there's a thin line here. Much of what was written in the past as "Negro dialect" was racially-stereotyped, and often inaccurate. Did black people ever actually say "gwine," or was that a white misconception?

I grew up in Wisconsin. When I tell people that, they put on what they think is a Wisconsin accent and pronounce it "Wiscansin. They say that's the way Wisconsinites talk, but I never heard a Wisconsinite talk that way. And while they insist that the "o" in Wisconsin is pronounced by the locals like a short "a," they never seem to notice that the locals pronounce "Milwaukee" with a silent "l" - muh-WOK-kee or MWOK-kee.

I think it's fine and necessary to put on a slight ethnic affectation when singing a song from another culture - but still I think it's important to avoid racial and ethnic stereotypes. It would be ridiculous to render "Old Man River" in a way other than "he don't say nothin.'" To my mind, "he don't say nothin'" falls within the broad spectrum of Standard American English - but the "shuck and jive" stereotyped dialect of blackface minstrel songs and of early movies (Amos & Andy, and the black dancer in early Shirley Temple movies, for example) is downright offensive. Despite what John on the Sunset Coast may think, much pre-1960 "Negro dialect" is a stereotyped and denigrating caricature that is very weakly rooted in reality. Interestingly, that exaggerated "dialect" was often used even by black performers before 1960.

-Joe-