Conan O’Brien gets back to reality

The best documentaries about people who live their lives in public uncover the real person behind the celebrity. In an online, all-access culture, it’s hardly a challenge to reveal where people live or their favorite snacks. Successful nonfiction films explain how and why extraordinary individuals do what they do. Three new documentaries dig for such honesty with varying degrees of success.

Conan O’Brien Can’t Stop unexpectedly discovers some dark sides to the famously sunny, self-deprecating talk show host. O’Brien’s been on television nonstop for nearly two decades, but the film begins at one of his lowest ebbs, shortly after he quit “The Tonight Show” rather than see it bumped to after midnight to make room for previous host Jay Leno.

Can’t Stop follows O’Brien from the conception of his 2010 “Legally Prohibited From Being Funny on Television Tour” through its final performance in Atlanta. We see a little of his onstage comedy and a lot of his rockabilly performances, but it’s more of a tour film that takes O’Brien’s temperature backstage and on the road.

When O’Brien cracks annoyed jokes to his staff about an excess of butter on his carryout meal, his faux-tyrannical reactions seem less and less feigned. He’s kidding, but he’s not really kidding. When “30 Rock’s” Jack McBrayer stops by his dressing room, O’Brien lays in with so many redneck jokes, he seems downright vicious. Already a perfectionist, he’s angry at NBC and increasingly exhausted due to his travel schedule. The movie audience starts to share his claustrophobia when the comic is surrounded by needy fans at post-show meet-and-greets.

Last year, NBC’s treatment of O’Brien made the performer the most sympathetic zillionaire in showbiz, but the documentary points out that some of his agita is self-inflicted. Instead of resting on his days off, he inevitably plays small, surprise gigs for his fans. O’Brien comes across as a comedy junkie, who loses almost more than he gives back.

To see possibly the most well-adjusted man in America, consider gentle horse trainer Buck Brannaman in Buck. Brannaman has two claims to fame: As children, he and his brother were rodeo stars famous enough to appear in cereal commercials and “What’s My Line?” Now a nurturing horse trainer, Brannaman served as a resident expert for the film The Horse Whisperer, as Robert Redford recounts in the documentary.

Buck and friends describe his horrifying treatment at the hands of his alcoholic, abusive father. Clearly, Buck’s childhood trauma informs his grown-up treatment of horses, which emphasizes communication over punishment and force. The films sets a leisurely pace as Buck drives around small-town America holding horse clinics.

Just when the film seems to be slowing to a halt, the final half hour focuses almost entirely on Buck’s work with a dangerous, poorly raised stallion. The moments with the “attack horse” prove nearly as suspenseful as the bomb-disposal scenes from The Hurt Locker. An iconic Western figure comfortable referring to “Oprah” and iPods, Brannaman emerges as a role model through his character, not just his achievement.

Rejoice and Shout examines not an individual person but an entire genre. Don McGlynn’s digest of more than a century of gospel music contains all the raw material you’d find in a Ken Burns documentary, but without the shape or narrative drive. Rejoice and Shout features plenty of expert talking heads as well as chatty gospel musicians and fans such as Smokey Robinson, but takes less a personal than a historical perspective.

The film authoritatively spans from its roots in plantation music to contemporary Christian hip-hop and explains the evolution of the sound, such as how the Swan Silvertones popularized falsetto singing. Rejoice and Shout stints on illuminating anecdotes, but features some amusing details, like the rivalry between the Blind Boys of Alabama and the Five Blind Boys of Mississippi.

Rejoice and Shout serves as a kind of jukebox of great performance clips, from national treasure Mahalia Jackson to lesser-knowns like Sister Rosetta Tharpe, who sings “Down By the Riverside,” then segues into a guitar solo worthy of Chuck Berry. The film’s academic ambitions cover too much ground, but the archival shots deliver their own insights. The sight of impassioned singers in the pulpits and church ladies enraptured in the pews are worth the words of a thousand interviewees.