This year's South by Southwest is Christmas in March for Texas music fans, with three major documentaries about some of our favorite cult artists — four, if we grant Oklahoma City temporary status as an annex of the Lone Star music scene. (Deep down, they'll be happy to get it.)

But watch the movies in the "24 Beats Per Second" program, and a heartbreaking sub-theme emerges: Viewers might begin to suspect that this year's fest was underwritten by a mental health advocacy group, one bent on encouraging music lovers to take good care of the fragile artists in our midst, lest they self-destruct or become strangers even to themselves.

Sure, the schedule includes straight-ahead performance films, such as "Scratch: All the Way Live," director Doug Pray's follow-up to his 2001 portrait of turntable virtuosity, "Scratch." And it offers chunks of optimism — such as "Press On," about pedal steel star Robert Randolph, and "Rock School," which may produce déjà vu for Richard Linklater fans.

It offers straightforward love letters, too: short films such as "The Ramones and I" or the ambitiously titled "Faded Love: The Life & Music of Bob Wills," that are minor but likable tributes to beloved musicians.

But the meat of the lineup centers on tragic figures who died too young, vanished into obscurity, or struggled throughout their careers with demons that kept them from the success they deserved.

In one case, a songwriter is being honored by multiple parts of the festival: Roky Erickson (of the 13th Floor Elevators) is the subject of the film "You're Gonna Miss Me" and of a panel discussion during the music festival. A famous casualty of LSD and schizophrenia, Erickson has been largely absent on the music scene since the late '60s.

Drugs take over

Drugs pop up, too, in the story of Oklahoma's Flaming Lips. Bradley Beesley's "The Fearless Freaks" begins with a super-cool blast of psychedelic imagery but quickly settles down to portray a place where minor-league crime is nothing to get worked up about. At times it seems like every member of the band has a brother in jail, a neighbor who's a crack fiend or, worse, a drug habit hiding in his own closet: Out of the blue in the film's second half, we see drummer Stephen Drozd sit down and prepare a hit of heroin while he matter-of-factly describes how he acquired his life-threatening habit.

That scene is harrowing, and it leads into a wrap-up that smacks a bit of "Behind The Music," but what precedes it is an engaging portrait of a band that seemingly should never have become as good as they are.

Beesley, a longtime friend of the Lips who has shot many music videos for them (he moved from Oklahoma City to Austin three years ago), says making the leap from MTV shorts to feature film was "an organic process. I would always keep the cameras rolling on the 'non-music video' moments, and in about 1996 started bringing a video camera to all the music videos to capture the making of. In many ways we have been collaborating for 15 years."

Love of Townes

The high point of "24 Beats," both in terms of filmmaking and of musical substance, is "Be Here to Love Me," a moving portrait of Townes Van Zandt by Austinite Margaret Brown. It begins with an ominous pronouncement from the songwriter himself, as he tells an interviewer that he has "designed it" so that his life would run out before his work does. Hearing how that design was realized — as witnessed by friends and family, in home movies and vintage interviews — can be painful, but it paints a fuller picture of Van Zandt than the one most of us know: how a high-achieving kid suffered some behavioral problems that were made far worse by institutionalization and how that damaged young man eventually decided that mastering his art was worth "blowing everything off."

Brown was late to discover Van Zandt — "I never met him, I never saw him play; it was only through vinyl," she says — but she became obsessed with him and wanted to tell his story without forcing it into a mold. She drew inspiration from "Thirty Two Short Films About Glenn Gould," the unconventional 1993 film that approached its subject through dramatized vignettes.

"I mean, that isn't anything like my movie," she says, "but — the way I think it is like my movie is that I didn't want to make any kind of biopic that told, you know, 'The Rise and The Fall and the Rise Again of . . .' I wanted to do something that challenged the viewer more. For me, the big question of the movie is: Would I do this? It's about a guy who gives everything up to live his art, to write songs. Everything else falls away."

Songwriters love to talk about Townes Van Zandt, and Brown found plenty of them — from Joe Ely and Willie Nelson to Guy Clark. But the film is best at impressing newcomers with the haunting quality of Van Zandt's art when it places a song or interview fragment over atmospheric footage shot by cinematographer Lee Daniel. For a singer whose legend is wound up in the mythology of the wandering troubadour, these images of back roads seen through dusty windshields are evocatively appropriate.

Seen but not heard

Jeff Feuerzeig works hard to get his imagery right, as well. In "The Devil and Daniel Johnston," the filmmaker meticulously re-creates the lonely bedrooms and impromptu garage studios where the songwriter recorded his low-fidelity masterpieces. Johnston's music and reputation have traveled the world, thanks to celebrity fans such as Kurt Cobain and Yo La Tengo, but the songwriter, who lives in Waller now, spent most of his time in a hermetic world of comic books and junk food.

Like Errol Morris in "The Thin Blue Line," he spends a lot of time showing us cassette tapes as they unspool — an obvious choice when talking about a man whose legend grew through the tapes he gave to everyone he met. Feuerzeig does a great job of organizing the many stories of Johnston's manic-depressive misadventures into one coherent narrative. But viewers who aren't already convinced of Johnston's songwriting brilliance may not see what all the fuss is about, as the best examples of his music are either unheard here or played in snippets.

If "Johnston" doesn't completely make its case, Josh Rubin's "Derailroaded" is much less persuasive. The story of Frank Zappa protégé and Dr. Demento fave "Wild Man" Fischer, it barely even tries to prove that Fischer's fans aren't simply voyeurs enjoying the fruits of his mental illness. The awkward performances here and the cringe-inducing footage of Fischer's more paranoid moments may dredge up sympathy for the man, but are unlikely to win any new fans for his music.

They are, however, an excellent advertisement for the services of a mental health professional. Audiences may flock to "24 Beats Per Second" for the music, but they'll come away with a deep appreciation of those who care for our most vulnerable neighbors.