In a better world, a film about Mavis Staples' journey from gospel singer through soul artist to living legend would have been made when she was in her prime.
In this routine, fitfully inspiring documentary, she's 76 - in one scene she returns to the Newport Folk Festival 50 years after appearing with her family's gospel group - and some of her present-day performances are a little over-egged.
As a retrospective, though, it's a tribute as richly deserved as the exclamation mark in that title. Staples' rich voice - she did baritone, contralto and blood curdling howl - was the major asset of the oddly named Staple Singers, who moved from Chicago churches to the recording studio in the early 1950s.
Those who remember Mavis' spine-tingling reading of a verse of The Weight in The Last Waltz, will also recall who sang next: Roebuck "Pops" Staples, the paterfamilias, who died in 2000, was the group's founder and his steady gentle presence rightly saturates the film.
In one deeply moving scene, Jeff Tweedy from Wilco, remastering old material, separates Pops' guitar and voice tracks to play to Mavis; for a moment, he's there in the room with them and her "I miss him so much" really hits home.
But there are few such magic moments.
Edwards has a tendency to over-direct rather than trust her talent, even when that talent gives lines like "this is the best time I've had since I got my knees done", so there's sometimes a sense of boxes being ticked. Still, the survey digs up lots of footage and usefully positions Pops as a quiet driver of the civil rights movement.
There are some excellent talking heads (including Bob Dylan, shot from an inexplicably high angle so you can hardly see his eyes) who provide useful analysis of the artists' position in the social, political and musical landscapes.
It falls short of being a great film, but it's a good one, about a great singer.
Review: Mavis! Documentary
Director: Jessica Edwards Running time: 80 mins
Verdict: What a gal!