Stax Records did not choose timid singers. The tour lineup was all belters — Redding, Sam & Dave, Eddie Floyd and Arthur Conley — who bounced percussive phrases off the band’s unswerving beat. They were R&B troupers from an era when performers didn’t need to lip-sync when they danced. The Stax singers commanded the stage with moves no choreographer taught them, and they didn’t rest until their audience became an ecstatic congregation.