A stage adaptation of the 1972 movie about a Jamaican singer turned outlaw hero sounds great but falls hard at the Public Theater.It looks like such a bright, sunshiny day as the lights rise on “The Harder They Come,” the reggae musical that opened on Wednesday at the Public Theater. The patchwork vibrancy of Kingston, Jamaica, where the story takes place, is efficiently and joyfully sketched in a tin-sided, palm-fronded, louvered and latticed streetscape, lit in happy yellows and purples and bursting with people wearing island florals. And when we meet our hero, the “country boy” Ivan, who has come to the city to seek his fortune as a singer, he is bubbly and hopeful, with a bubbly and hopeful opening number to match: “You Can Get It If You Really Want.”But can you?Alas, over the next two hours or so, the answer will prove to be no, not just for Ivan but also for the audience. Like the chaotic 1972 movie it’s based on, which helped introduce reggae to audiences beyond Jamaica through the songs and charisma of Jimmy Cliff, the musical, adapted by Suzan-Lori Parks, is yanked apart by irreconcilable aims. The uplift of the infectiously danceable tunes keeps obscuring what turns out to be a deeply unsunny story.Not that the movie, directed and co-written by Perry Henzell, was very clear to begin with. Though considered a landmark by many, and certainly a point of national pride for Jamaica, it cannot count narrative logic as one of its strong suits. Its fascination is more like that of a fable, tracing the quick, jagged course of Ivan’s descent. Barely off the bus to visit his mother, he’s robbed of his meager belongings; soon thereafter he’s robbed of his soul, forced to sell his first song for just $20.Conflicts with the church (he falls for Elsa, a preacher’s ward), the police (he’s punished with lashings for defending himself) and even the ganja trade (what do you know, it’s corrupt!) gradually turn his disillusion into derangement. By the time this Candide becomes a semi-psychotic outlaw idol, like the characters in spaghetti westerns, it’s hard to keep track of the chain of injustice or even just the genre.If it’s easy to see why Parks might have wanted to work with this rich material — the movie’s soundtrack is deservedly a classic — it’s also clear that it needed rethinking for the stage. Yet her adaptation is full of choices that, however sensible they seem at first, ultimately make the problems worse.To give the story larger and more legible implications, she pushes the loosely drawn characters of the movie toward greater extremes of badness and goodness. The preacher is not just a hypocrite but a full-blown Judge Turpin, all but slavering over Elsa. The payola-scheming music executive and the police officer who controls the drug cartel are not just grifters but sharky megalomaniacs.Jones as Ivan and Meecah as Elsa, lovers in the movie whose courtship in the musical takes a more conventional turn.Sara Krulwich/The New York TimesAt the same time, Ivan (Natey Jones) is radically softened, as if the muddled moral middle ground were a dangerous place to locate a musical. His braggadocio is sanded down to mere optimism, his crimes minimized and justified to emphasize his essential innocence. This takes a bizarrely conventional turn in his courtship of Elsa, whom he doesn’t merely shack up with but marries.Evidently the idea is to downplay the characters’ complexity and culpability in favor of an overtly political interpretation of the story that the movie, in its laid-back way, was mostly content to suggest without comment. Parks’s script, and the staging by Tony Taccone and Sergio Trujillo, heavily underline the larger forces — colonialism, capitalism, racism — that help explain or even require Ivan’s bad choices.Though that’s perfectly valid in theory, the heavy-handedness is quite a surprise coming from Parks, whose greatest plays float at the midpoint between archetype and individual. “Father Comes Home From the Wars” superimposes Homer’s “Odyssey” on the tale of a Black man who buys his freedom by fighting for the Confederacy. “Topdog/Underdog,” which won the Pulitzer Prize and was recently revived on Broadway, pulls off a similar balancing act in telling the story of hustling Black brothers named Lincoln and Booth.That balance has been thrown off in “The Harder They Come.” One reason is that the original was a movie with songs, and the songs were all diegetic: They arose from situations in which characters were actually singing, in a church or nightclub or recording studio. But because Parks was writing a musical, the songs had to do and be much more. The movie’s short tunestack — really just four or five main numbers — would have to be expanded.Still, it was another reasonable idea that backfired to expand it quite this much: There are 33 numbers listed in the program. About a dozen are by Cliff, from the movie or elsewhere; several are by other songwriters of the period; and three quite good ones are by Parks herself. (In her non-playwriting life, Parks fronts a “Modern Soul, Black-Country, Psychedelic-Afro-Righteous” band.) They’re deftly arranged for eight musicians by Kenny Seymour.But to accommodate so many, most are reduced to mere atmospheric snippets, curtailing their effectiveness. Even when they are pushed toward more prominence, they tend to evaporate on contact, as they’re forced, like the songs in jukebox musicals, into uses for which they weren’t designed. The rhythmic groove that makes reggae so intoxicating prevents the kind of development that edges a character forward, just as the repeated chorus structure, usually with repeated lyrics to match, stalls when deployed as drama.J. Bernard Calloway rattles the rafters with “Let’s Come in the House,” our critic writes.Sara Krulwich/The New York TimesAt least the songs are sung well: Jones is as beamish as his music sounds; you can see and hear how his Ivan might be the star the show says he is. Meecah, as Elsa, and Jeannette Bayardelle, as Ivan’s mother — both roles greatly expanded to counteract the episodic nature of the underlying material — take full advantage of their brief vocal moments to shine. As the preacher, J. Bernard Calloway rattles the rafters with “Let’s Come in the House,” a terrific gospel shout. The rest of the ensemble backs them up appealingly, and dances Edgar Godineaux’s choreography even more so.Still, the promise of the show, like the promise of its opening imagery — sets by Clint Ramos and Diggle, lighting by Japhy Weideman, costumes by Emilio Sosa — goes largely unfulfilled. Neither its satire of criminal celebrity nor its tragedy of sullied innocence nor even the sonic pleasure of its catchy score escapes the distorting gravity of its oversized intentions. Instead, “The Harder They Come” falls right into the trap of the rest of that title lyric: “the harder they fall.”The Harder They ComeThrough April 2 at the Public Theater, Manhattan; publictheater.org. Running time: 2 hours. More