“The Harder They Come” is one of those cult classic movies that tapped into multiple veins in the zeitgeist at once. The 1972 indie was an immediate hit in Jamaica, where it was shot vérité style, then found a rapturous reception at that summer’s Venice Film Festival, where it was picked up by Roger Corman’s New World Pictures and became an art-house sensation in the States. As Roger Ebert noted at the time, the film is really a two-fer: a by-the-numbers Blaxpoitation film in a novel Caribbean setting and, more interestingly, a celebration of Jamaican culture and reggae music that was beginning to find a broader worldwide audience.

Now Suzan-Lori Parks has adapted the film for the stage, fleshing out film’s loosey-goosey plotting with some more conventional narrative structure and turning it into a more traditional musical, boosted by Jimmy Cliff’s original songs as well as a few new ones of her own. She positions our antihero Ivan as a recognizable musical-theater type: the country-bumpkin striver who lands in the big city (Kingston) with guitar case and luggage in hand hoping to make it big.

British actor Natey Jones (Get Up Stand Up) oozes charisma as Ivan, and even manages to one-up Cliff vocally as he delivers the reggae giant’s classics with a soaring voice that doesn’t need amplification to reach the back row of the Public Theater (where the show opened Wednesday). His determination to get ahead shines from scene to scene, whether it’s finding ways to defy the local music boss who won’t let him play his music or winning over a young church-going girl (Meecah) whose preacher guardian (J. Bernard Calloway) has been planning to woo her himself.

What Parks can’t quite resolve is the sudden shift in tone as this sweet country boy turns outlaw (admittedly, a less hardened or blood-thirsty criminal than the film version’s). The transformation is a problem for the movie as well, although there the actor Cliff makes no effort to appear endearing from the outset and clearly articulates a desire for fame and fortune at any cost. (Jones’s portrayal of Ivan in the first act, meanwhile, gives no hint of the character he becomes after intermission.) The dichotomy may be best exemplified in the film and show’s two most famous (and oft-reprised) songs: The genial, lilting “You Can Get It If You Really Want,” which fits snugly in Broadway’s “I wish” genre though the object of desire remains vague, and the more defiant title song, an anthem for defiance and pushing boundaries that helps propel Ivan into a Robin Hood-like folk hero.

The cast is uniformly excellent, especially vocally, under the direction of Tony Taccone and Sergio Trujillo; standouts include Meecah as Ivan’s level-headed bride, Calloway as the deep-voiced hypocrite of a preacher, Jacob Ming-Trent as Ivan’s best friend and Dominique Johnson as the local ganja-dealing kingpin. (Purists may quibble about Kenny Seymour’s arrangements, which sometimes put the lilting rawness of reggae through a more polished Broadway orchestra filter.) And the production numbers get a visual lift from Edgar Godineaux’s booty-shaking choreography, as well as Emilio Sosa’s costumes and a production design, by Clint Ramos & Diggle, that evokes Jamaica with its corrugated-steel siding and splashes of color.