Roy Orbison, for sure. Also Mary Fahl, Gordon Lightfoot, Lowell George, Ralph Stanley, Van Morrison, Elvis Presley, Stan Rogers, Sandy Denny, Steve Perry, Tim Obrien, Paul Robeson, Paul Rogers, Norah Jones, both Everlys, Nat King Cole, Ella Fitzgerald, Vince Gill, Patsy Cline.
How's that for diversity?