Woodstock may have taken place 40 years ago, but the Oscar-winning film that chronicled that landmark event — along with such features as “Don’t Look Back,” “The Last Waltz” and “Stop Making Sense” — set the bar so high that few music-driven documentaries in their wake have measured up.

These works gave viewers front-row access to historic events and artists, capturing the public’s imagination in lasting, significant ways. But as popular music becomes ever more homogenized, and today’s American Idol becomes tomorrow’s afterthought, the mystique that enveloped artists like Hendrix, Dylan and the Band has been relegated to nostalgia.

Much of it has to do with round-the-clock access to popular music via cable and the Net, with sites like YouTube and Wolfgangsvault offering free streaming and downloads of rare and vintage performances that were once the exclusive domain of bootleg collectors, not to mention the increasing audio and video sophistication of home theater systems.

But then music-based pictures have always been a tough sell. “Music documentaries weren’t doing so great theatrically even when the economy was doing great,” says Brad Abramson, VH1 VP for production and programming.

Indeed, theatrical runs almost never mine box office gold and are very seldom profitable: “Shine a Light,” directed by Martin Scorsese, grossed only $5.5 million domestically, while “U2 3D” has scared up $9.7 million to date. And pity the poor Jonas Brothers, who were lambasted when the trio’s “Jonas Brothers: The 3D Concert Experience” grossed a paltry $12.7 million in its first week.

Theatrical runs are increasingly viewed more as a way to brand the film before it goes to DVD or TV than as an attempt at making money.

“Let’s face it: Your theatrical life is a short one,” says “Stop Making Sense” director Jonathan Demme, who is now shopping “Neil Young Trunk Show.” “More people will end up seeing it at home (on DVD) or on broadcast than at the theater. It’s the way movies are consumed in 2009.”

With more people using their TV screens as their computer screens or fiddling with handheld devices, options continue to expand as theatrical windows for music docs grow ever smaller. For example, a documentary on Montreal-based band Arcade Fire, “Miroir Noir,” was being streamed free of charge for one week only earlier this month on Pitchfork: TV — a price that can’t be beat.

Distribution can be hard to come by if there is not a superstar artist and/or big-name director attached.

Denny Tedesco spent more than a dozen years making “The Wrecking Crew,” a documentary on the legendary group of L.A. session musicians who played behind everyone from the Beach Boys to Sonny and Cher and the Righteous Bros. Tedesco has screened the doc at more than 40 film festivals, taking home top honors at many of them.

But he has yet to find a taker, in large part because of the low- six-figure licensing fees for the more than 130 song snippets used. Tedesco stresses the labels and publishers have agreed to let their music be used at a discounted rate, “but we’re still trying to raise the money for that,” he says. Otherwise, he fears his labor of love is “dead in the water.”

“We’re only interested if (the project) is completely done,” concurs Tom Bernard, Sony Pictures Classics co-president and co-founder. “Come to us pre-cleared and everything taken care of.”

The Sony specialty arm has two upcoming music films on tap: “Soul Power,” the story of the historic 1974 concert by James Brown, B.B. King and others in tandem with the Mohammad Ali/George Foreman “Rumble in the Jungle” fight in Zaire (bowing July 10 in New York and Los Angeles); and electric guitar doc “It Might Get Loud,” directed by Oscar winner Davis Guggenheim and starring the Edge, Jack White and Jimmy Page (Aug. 21).

Bernard adds that he would “probably not” pick up a straight performance film from a current act now: “I think people would rather go see the concert,” he says. “I was involved years ago in the midnight movie biz. People would go see (concert films) by Led Zeppelin, Genesis, Blue Oyster Cult (on) a Saturday night.” He notes those days are largely gone.

Nevertheless, rock and metal still provide fertile ground for documentaries. “Flight 666,” a film about Iron Maiden, won the 24 Beats per Second prize at the SXSW Film and Music Festival in Austin in March. Distributed by D&E Entertainment, the film will open in more than 40 theaters nationally April 21.

But when it comes to appealing to distributors, even the legendary Lizard King can use a helping hand. Director Tom DiCillo took 100 hours of vintage footage and shaped it into “When You’re Strange,” a documentary about the Doors. The film, which DiCillo says “allows us to see the band almost as if they’re immortal,” has aired at a number of festivals but is being retooled with narration by Johnny Depp. “Once we got Johnny Depp, we just decided to start afresh. We all feel it will be a huge leg up,” says DiCillo, who writes about the project on a blog at tomdicillo.com.

“When You’re Strange” is DiCillo’s first nonscripted film, unlike Demme, who has toggled back and forth between dramatic features and music docs throughout his career.

Demme calls “Trunk Show,” an intimate performance film, the “stylistic response” to the more formal “Heart of Gold,” his 2006 Young pic. “I like to warn people that if you aren’t into Neil Young and you’re not into serious electric guitar, don’t come.” Demme’s next film will focus on Bob Marley.

A compelling story can come from anywhere, Abramson says. VH1 has acquired the exclusive television and DVD rights to “Anvil! The Story of Anvil,” as part of its popular Rock Docs franchise. VH1 also heavily will support a theatrical distribution of “Anvil!” by Abramorama. “Anvil!,” the true story of a heavy-metal band trying to come back from obscurity after the release of its 1982 album, “Metal on Metal,” marks only the second Rock Doc to receive theatrical play.

VH1 runs up to eight new Rock Docs per year. They comprise a mixture of acquisitions (with airing rights for up to five years), co-productions and inhouse productions.

As a way of mitigating costs, VH1 has pacted with the History Channel to present “Woodstock: 40 Years Later,” directed by Oscar winner Barbara Kopple, in August.

In many ways, those three days of love, peace and music continue to generate sparks among filmmakers. While Kopple’s film looks at the legacy of Woodstock via ensuing concerts that took its name, director Ang Lee has dramatized the events and personalities that led up to that epochal concert with the recently wrapped “Taking Woodstock.”

“We’re splitting the cost and we’re simulcasting it,” Abramson says of the Kopple film. “It was a big-ticket item.”