Despite little outward resemblance, the actor worked for months to get the look, sound and movement right for the new film “Bob Marley: One Love.”

A report by Rob Tannenbaum for The New York Times.

Bob Marley, the beloved and singular reggae luminary, was a dreadlocked Rastafarian from Jamaica who sang and played guitar. Kingsley Ben-Adir is a Brit with close-cropped hair who doesn’t sing or play guitar, and stands seven inches taller than Marley did. Despite the lack of external similarities, Ben-Adir was cast as Marley in a new Hollywood biopic, the culmination of a yearlong search for the right actor.

“We tried to find someone from Jamaica who could speak the dialect we needed,” said Ziggy Marley, Bob Marley’s oldest son as well as a Grammy-winning musician, and a producer on “Bob Marley: One Love,” which opened in theaters on Feb. 14. But physical verisimilitude, he decided, wasn’t the key to portraying his father: “Kingsley brought an emotional depth that nobody else brought to the auditions, and a magnetism,” he added.

The choice of Ben-Adir has been denounced by many Jamaicans, who point out that at least since 1990s films like “Cool Runnings” and “How Stella Got Her Groove Back,” Hollywood has been using non-Jamaican actors with diluted accents. “We were not meant to have agency over our narratives,” Danae Peart wrote in RiddimStyle Magazine, which covers culture in the Black diaspora. She added that Hollywood executives are obsessed with “making everything palatable for the ‘white gaze.’”

Reviews for “Bob Marley: One Love” have been almost uniformly negative, but even some of the harshest critics have praised Ben-Adir’s performance. “In a film that mostly sticks to reliable formula, he is one thing to love,” Olly Richards of Empire wrote. Recently, Ben-Adir explained in detail how he made the transformation, despite little outward resemblance to Marley.

Landing the Role

“On the audition tape, I knew that my Jamaican patois was going to be basic and wrong,” Ben-Adir, a lean, alert 37-year-old dressed in a dark Adidas track suit, said during an interview in a Times Square conference room. He chose one scene from among three he’d been sent, and had only two days to prep his audition — not enough time to nail the accent. “Working actors don’t have the luxury of time and space.” He crammed by studying “Live at the Rainbow,” a Marley concert video shot in 1977.

The Marley family was closely involved in the movie: Ziggy, Marley’s daughter Cedella, and his wife, Rita, are all producers. Shortly after seeing his audition, they asked to meet Ben-Adir. “There was something about the family being involved where I felt like I could let go of the responsibility of the whole thing and focus on finding the emotional truth.”

Nailing the Music

Ben-Adir had less than a year to transform himself. “I was like, Nine months? You need five years!” He bought an acoustic guitar as soon as he finished filming the Marvel mini-series “Secret Invasion,” watched YouTube instructional videos, and played “Redemption Song” over and over “like a lunatic” before hiring a guitar teacher. Producers told him he didn’t need to learn to play and said they could shoot around it, but Ben-Adir felt it was crucial to understand Marley.

Singing was a steeper challenge. Ben-Adir doesn’t even like karaoke, and in drama school, when teachers praised his singing voice, he realized they were lying to make students more confident. In the movie’s concert scenes, he lip syncs to the original recording, but elsewhere, he plays guitar and sings. He thought Marley’s sons Stephen, who served as music supervisor, and Ziggy would dub his vocals, but thanks to work with a voice coach, Fiora Cutler, he sounded good enough to handle the job himself. “I can hold a tune,” he said proudly.

Getting the Look Right

“I realized that I’d never look as close to him as I want, so I had to let it go,” Ben-Adir said. “Bob was flat-chested and doesn’t have broad shoulders, and I’m the opposite, with skinny stick legs and a chest that pops. As soon as you put me next to someone who is 5-6, I’m going to look like a giant, no matter what costume I’ve got on.” (Ben-Adir is about 6 feet 2 inches.)

Nine months wasn’t enough time to grow dreadlocks, so he wore a wig instead. Ben-Adir singled out the hair and makeup artists Carla Farmer and Morris Aberdeen: “It was one of the hardest things to get right, and they did an incredible job.”

Getting the Accent Right

In his research, Ben-Adir observed that Marley was adept at code-switching, varying his tone and vocabulary depending on the situation. “If Bob didn’t like you,” he said, his patois would “get so heavy, you can’t understand what he is saying.”

At times, Ben-Adir felt as though he might as well be doing the film in French, which he doesn’t speak. During downtime on the “Barbie” shoot (he was one of the Kens), he studied Marley’s accent. “I became obsessed.” Once filming started, he leaned on the Marley family and Neville Garrick, Marley’s close friend and art director, who is credited as the film’s historical adviser, to settle into the right level of patois. He also studied Marley’s unusual manner of moving onstage, which Ben-Adir described as a way of conducting the band, as well as other physical tics, including the musician’s habit of talking out of the corner of his mouth to express quiet disgust.

Gaining Insight

Ben-Adir spoke to “60 or 70 people who knew Bob personally,” he said. Some of the people closest to Marley refused to meet him. “Not everyone is going to trust me, because I’m ‘an English bwoy,’” he added in patois. “I get it. Bob means so much to so many people, and they still have a lot of pain that he died so young.” (The star died of cancer at age 36, in 1981.) Others talked evasively about Marley, using only trite, unhelpful sound bites.

The movie begins in 1976, when Marley is already the biggest star in reggae. He survives what may have been a politically motivated murder attempt at his home, then goes into exile in Britain, where he records “Exodus,” the album that makes him a global superstar. “I understood that the internal journey of Bob had to be about safety. The film is an exploration of trauma, and what it means to feel like you’re not safe or not loved in your own country,” Ben-Adir explained, adding, “He needed music.”

Ben-Adir has a white father (as did Marley, though his father left the family soon after Bob was born) and a mother of Trinidadian descent, and for the most part, he doesn’t talk about his personal life. But he made a brief exception to explain how he found common ground with Marley.

“I didn’t tell the family this, but I spoke to a lot of psychologists about where me and Bob meet. I landed on safety,” he said. “There are a lot of things my friends don’t even know. From as far back as I can remember. I didn’t have a sense that it’s all going to be OK.”

He explained, “The witnessing of violence at a certain age, and how that affects trust and safety — that was really what my investigation with Bob and myself was. It was violence.”