Kwame Kwei-Armah didn’t want to be a Bob Marley fan. For a start, his big sister was into reggae, which put him off. What’s more, as he was growing up in London in the 1970s, white kids were forever coming up and asking “Are you jammin’, mon?” or “Do you want your doughnuts with jammin’?” They’d call him golliwog and sambo, too.

“It used to really freak me out,” he says, on a break between rehearsals of the world’s first Bob Marley musical, One Love, which he has written and directed. “My natural instinct would be: there’s more to me than just whatever you know about black culture. So I disassociated myself from anything Bob-like.”

Then came his political awakening at the age of 19. “Bob became a hero, almost my personal poet laureate. He was someone who could speak truth to power in a beautifully articulate but melodic fashion. Not just anyone can say: ‘Emancipate yourself from mental slavery.’ The melody allows the words to bypass my critical faculties and find their way into my bloodstream.” Kwei-Armah later traced his Ghanaian roots and rejected his birth name of Ian Roberts.

It took 10 years to get One Love off the ground, not least because Marley’s family didn’t want his story to be told in a film or play. Finally, however, they green-lit Kwei-Armah’s idea and 2015 saw its first iteration sell out at the Center Stage theatre in Baltimore, where he has served as artistic director since 2011. During the show’s run, uprisings in the city were sparked by the death of Freddie Gray, a 25-year-old black man, in police custody. “We took parts of the show out on to the streets,” says Kwei-Armah.

A new version is about to open at Birmingham Repertory theatre and, as we talk, the team are entering the final week of rehearsals. The practice room has one mirrored wall and another that’s mostly window, while the edges of the grey rubber floor are strewn with bags, water bottles and plastic guns. The cast, dressed in a selection of slouchy dancewear and knee supports, are performing the closing scenes for the umpteenth time.

Kwei-Armah watches intently, regularly interrupting if lines aren’t spoken clearly, or to go over the motivation or subtext of certain exchanges or dance routines. Mitchell Brunings, who was born in Suriname and raised in the Netherlands, plays the lead and renders Marley’s songs seemingly effortlessly. Even without costumes, set and special effects, and with only an electric piano for accompaniment, the harmonies, action and emotion of the cast are spine-tingling.

This show, says Kwei-Armah, is 50% different from the Baltimore run. “I don’t think I dug deep enough into what made Bob the man,” he says. “This production is Bob the deeper cut.” It focuses on the same era, though, from his courageous appearance at the Smile Jamaica concert in 1976, two days after the failed attempt on his life, to his time living in London afterwards, culminating in his return home for the 1978 One Love peace concert.

“The original catalyst to crack my way in,” says Kwei-Armah, “was the song Running Away, one of the first he wrote in London. Even though he wasn’t mortally wounded by the gunshots, his soul and his spirit were, in my humble opinion. And he chose London for exile – a London where punk was in its ascendancy, and young British blacks were finding their identity. I thought, ‘What a brilliant time to set a play in.’ Bob in my home town, shopping in Shepherd’s Bush market.”

Marley was spectacularly prolific during this period. “He wrote Exodus, Kaya and lots of other stuff for future albums. Although he was in existential pain, that just seemed to contribute to his muse.” Kwei-Armah’s research naturally took him to Jamaica. Driving around Kingston, he laughs, “nearly everyone I met was either the catalyst for a song or gave him a couple of lyrics. Someone would say, ‘Yeah I was sitting with Bob and the cornmeal porridge was boiling and I said, Bob, look, go stir it up.’”

His visit to Marley’s mausoleum had a profound affect on him: “Just being in that room where his bones are interred. There was a brilliant guy looking after the tomb. When he spoke about Bob, I saw so much love. Not boastful about access to Bob, just total love. I’ve never forgotten it.”

The play is “absolutely not” a jukebox musical, says Kwei-Armah. “It’s not sing-along-a-Bob, but I’ve tried to use many of the rules of musical theatre: that you sing what you can no longer speak – the emotion that you have. I’ve got to make it feel like it’s a musical with a really rich book.”

In particular, he has explored Marley’s identity “as someone who was biracial, and how that played into his relationship with the original Wailers”. His religion, too, is examined: “How did he become Rastafari? What did Rastafari mean in relation to his songs and the way he viewed the world?”

Kwei-Armah says it’s natural as a writer to want to “go in again”. In America, it is standard practice to view each run as a work in progress. “August Wilson, one of my role models – his plays would do a 20-city tour before they got to Broadway, and he’d be fine-tuning all the time. So my exposure to the American dramaturgical tradition just made that natural, ‘Cool, we’ve got it standing. We can see it now. How can we make it better?’”

Center Stage has just reopened after a $32m renovation, which includes taking the theatre out to reach people around the city and beyond. “I didn’t come to theatre to play to the 1%, the 4% or just those who are blessed enough to have access to theatre or high arts.” Kwei-Armah, who spent five years in the cast of Casualty, is on something of a mission to make the “high arts” the popular arts.

“I’m dedicated to access for all. Are we creating diverse enough work in gender terms? Are we making the 70% of ticket-buyers who are women say, ‘I’m seeing myself as the protagonist’? Are we seeing people from different communities and their stories? That’s the stuff that excites me.”

Has he commissioned works responding to the new political climate? “Yeah a couple,” he says, “but it might be too early to speak about them.” However, he says one of the biggest things he’s learned from switching from playwright to artistic director is that “metaphor really is the most powerful instrument for art. So when Brexit happened, when Trump became president, I began to look for the classic plays that speak to this time or this feeling.” Bertolt Brecht’s Hitler satire The Resistible Rise of Arturo Ui is a great play for now, he says, as is JM Barrie’s The Admirable Crichton, about an aristocratic British family falling under the rule of their butler after they’re all shipwrecked on a deserted island.

But right now Kwei-Armah is looking forward to getting the cast on stage for proper technical rehearsals. “I often describe rehearsal as me helping the actors to do their thing – and then tech is my time, when I make the show. Put in the lights, the sound, bring everything together.”

Now that they’ve entered the home straight, he says, “we’re in the land of quantum leaps. Every run has to be a quantum leap better than the time before. I know there are about 15 car crashes ahead of me. I just have to keep my nerve and keep going, ‘OK, it is going to be better tomorrow.’”

• One Love: The Bob Marley Musical is at Birmingham Rep 10 March to 15 April. Box office: 0121-236 4455.