I'm a little confused about the "voice quality" thing,and whether that's a criterion, but if so, I'd certainly agree with Clinton about Garnet Rogers, and add John Gorka to the list of contenders. Then again if "quality of voice" rather than "voice quality" creeps in we have to start talking about Greg Brown, Jack Elliott, Bill Morrissey, Bill Staines, Tom Paxton, Geoff Bartley and a bunch of others still practicing. Given the tone of some of the tracks on Ragpicker's Dream Mark Knopfler is oozing into folk(ish) stuff more & more; and assuming blues fits in with folk we'd have to open it up tot he likes of Chris Smither, whose range from gravelly growl to reedy whine can make me shiver. And them's just off the top of the head. Arlo Guthrie.