It gets to you, watching R&B legends such as Sam Moore, Jerry Butler, the Chi-Lites, Carla Thomas and the names above dig deeper into the music they made in the Sixties and Seventies. Journalist Roger Friedman conducts the trenchant interviews -- Moore recalls his dark days as a drug pusher, then performs a killer "When Something Is Wrong With My Baby." Most touching is Thomas, who recently died at eighty-four, duetting with daughter Carla on "Night Time Is the Right Time." Documentarians D.A. Pennebaker and Chris Hegedus (Startup.com) blend insights with rare concert footage, creating one for the time capsule.