Over the years, The O'Jays' lineup has shifted, and so have R&B's dominant motifs. But the group's powerful harmonies—led by the soaring bellow of Eddie Levert—have remained constant, establishing a through line between late-'60s soul rave-ups like “Working On Your Case”, psych-tinged funk tracks like 1975's “Rich Get Richer” and new jack swing-era ballads like 1991's sumptuous “Keep On Lovin' Me”.