"I'll stop singin' when I have nothin' left to say," insists Mavis Staples early in Jessica Edwards' delightful documentary, and by all indications, that won't happen anytime soon. She's been doing it for over six decades, as part of the Staple Singers and on her own, riding a tide from gospel to folk to soul to rock to "Americana," and that journey is the primary concern here; her personal life is given rather short shrift, but that's a minor complaint for a film as high-spirited and good humored as this one. Staples is a wonderful storyteller (with killer comic timing), and her remembrances are supplemented by observers, home movies, and killer archival footage. She's a force of nature—a remarkable artist, paid appropriate due by this moving and entertaining picture.