Roberta Flack & Donny Hathaway

Roberta Flack covered a fair amount of ground in her ten years of commercial success: starting as a jazz-fusion stylist, she moved on to intricately-produced pop and even disco. You could argue that the gentle soul sound espoused by Flack, Donny Hathaway and others was R&B's answer to soft rock; you could also argue it just developed from the more contemplative work of Aretha Franklin and Otis Redding.

In any case, her crystal-clear voice and classy arrangements sold a pile of records and spawned a whole school of imitators. Since the late 70s she's struggled commercially, though she was been pushed back into the spotlight by a smash cover version of her signature song, "Killing Me Softly With His Song," by the Fugees.