A dramatic highlight of Kevin Macdonald’s documentary about Bob Marley, which opened nationally April 13, comes in a concert sequence from 1978, when the reggae star called the leaders of Jamaica’s two political parties, then embroiled in bloody street warfare, onstage to uneasily clasp hands in unity.Marley’s eldest son Ziggy, the film’s co-executive producer and himself a Grammy-winning reggae performer, sees the moment as a sign of his father’s power. “I think it was confusing to (the politicos),” he says. They were the leaders of the country. He was much bigger than they were.” Almost 31 years after his death from cancer in May 1981, Bob Marley still commands that kind of clout, although it’s commercial power rather than political or spiritual. The theatrical release of “Marley” — which is being accompanied by a day-and-date video-on-demand launch and a paid stream on Facebook — and its attendant soundtrack album, issued April 17 by Universal Music Enterprises, should light renewed fire under a seemingly timeless, and nearly priceless, music catalog. Bruce Resnikoff, president-CEO of UME, Universal Music Group’s catalog unit, says the worth of Marley’s music is quantifiable only in a greater context. “It’s clearly not only one of the most valuable music assets to Universal, but I think (it’s) one of the most important, valuable assets in the entire history of music.” Marley, who became reggae’s international star via his ’70s recordings with the Wailers for Island Records (now held by UMG), has shifted records posthumously in immense numbers. He was and continues to be marketed like a rock star, and no Third World musician has come close to equaling his numbers. The 1984 hits compilation “Legend,” his biggest title, has sold 11 million copies to date, according to Nielsen SoundScan. The set has logged 1,054 non-consecutive weeks on the national catalog chart, second only to Pink Floyd’s “Dark Side of the Moon,” the longevity champ. For the week ending April 15, it stood at No. 124 on the U.S. pop album chart (which currently reflects both current and catalog release), where it has spent 793 non-consecutive weeks. “You also have albums like (1977 studio album) ‘Exodus’ and (1999 remix album) ‘Chant Down Babylon’ that have scanned over 800,000 in the SoundScan era,” Resnikoff notes. “And remember, many of these albums launched before (1991), so there were significant sales even before the SoundScan era.” The potency of Marley’s catalog was reflected in Forbes’ 2007 ranking of the top-earning late celebrities, on which Marley placed 12th (between James Brown and James Dean), with earnings of $4 million. The “Marley” soundtrack, released simultaneously in two-CD and three-LP packages, should get an immediate lift from Macdonald’s picture, which was a critical and audience hit at the 2012 Berlin and SXSW fests. The two-and-a-half hour feature initially is hitting 50 screens in 20 U.S. markets, and an additional 15 to 20 screens in the Caribbean, according to Eamonn Bowles, prexy of Magnolia Pictures, which acquired the doc in February. But the company is not relying on theatrical play for its grosses, offering the pic via VOD out of the gate. “People do want to see films in theaters,” Bowles says. “We make it available to them in all these metropolitan areas. But the reality is, a lot of people can’t necessarily get to the theaters in a timely manner, and some people would like to see the films while they’re current and hot. Having it available on VOD is a great way to distribute it to a huge swath of people that the widest theatrical release could never get to.” Another interesting marketing wrinkle is the decision to offer “Marley” on Facebook for a limited time as a $6.99 paid stream; part of the proceeds will benefit Save the Children, the international charity. “Marley has 37 million fans on Facebook, Bowles says, “so it’s obviously a huge, huge, huge platform to market to, and whether they see it on a Facebook platform or not, just having that awareness of all those people who have liked Marley on the Facebook page is enormous.” While Bowles acknowledges that music documentaries have never been particularly robust performers theatrically, he adds that the craftsmanship of “Marley” and its rare candor should draw audiences. Indeed, the documentary touches on the most personal aspects of Marley’s life, most particularly his many mistresses and out-of-wedlock children, and his distance as a father to Ziggy and older sister, Cedella. Some oncamera participants, like Marley’s former Wailers mate Bunny Wailer and eccentric producer Lee Perry, were sometimes embroiled in legal wrangling with the Marley family. Ziggy Marley says the process of enlisting some of the estranged interviewees was delicate. On the label side, Resnikoff views “Marley” — the first new title issued by UME since its January settlement with the Marley family in a dispute over royalties and masters ownership — as an important new chapter in marketing an artist who can no longer reach his audience from the stage. “When you see this movie, you experience a part of his life and his music that you can’t get from just downloading the songs or buying the music,” he says. “I think it’s to a great extent much like an artist touring today, generating interest in new fans and regenerating interest in existing fans. … It’s also going to open the door to doing more interesting and creative things with the catalog.” Ziggy Marley views the film — finally reaching the screen after the departure of prospective directors Martin Scorsese and Jonathan Demme and five years in production — as “a document I can pass on to my children, and they can pass on to their children.” Asked about the similarly long-gestating prospects for a dramatic film about his father’s life, he says he sees a day when that will happen, but only far in the future: “We’re doing one step at a time,” he adds. Or as they say in Kingston, soon come, mon.