In this lively documentary about the titular nightclub that for decades lured blues musicians to South Central LA, the numbers are so electric one wishes director Ramin Niami had made a full-scale concert film instead of shooting his footage during the joint’s closing days. Former headliners like John Lee Hooker and Bobby “Blue” Bland have passed on, but their red-hot proteges tear up the stage between vivid recollections, like the one by Keb’ Mo’ about nervous white patrons ducking and running from their cars into the club. Fans weren’t the only jumpy ones: owner Laura Mae “Mama” Gross slept on a pool table with a .38 tucked away. (She lived to age 89.)