Toronto-based director Alison Duke never planned on making a documentary about Sister Nancy — the pioneering female dancehall and reggae artist whose 1982 hit Bam Bam has been sampled, interpolated and remixed by everyone from Groove Armada and Lauryn Hill to Kanye West. Instead, she says, the opportunity "fell in my lap."

Duke was working late one night when she got a phone call from one of Nancy's tour DJs, who also happens to be Canadian.

"He said, 'The only thing is, I want you to do this documentary, but Sister Nancy has to approve,'" Duke says. "Meaning Sister Nancy has to like you. And I'm like, 'OK, I'm all in.' The next thing you know, I was on a call with Sister Nancy, and she liked my spirit, I guess, and we started working with each other."

Several years later, the result is Bam Bam: The Sister Nancy Story, a film that looks at both Nancy's life story and her long fight to get the royalties she was owed. Duke says Nancy's story appealed to her for a number of reasons.

"I was just interested in her story because she's an older Black woman artist who's still going strong," she says. "She's still touring, she's still making music, she's still living her life as an artist. And I connected with that because I am an older Black female filmmaker [who's been] doing it for a while. I just didn't know, like, where her tenacity and her spirit came from. And so I was really interested in seeing that really close up."

Another reason was Nancy's music itself. Bam Bam was a favourite tune of Duke's when she was a teenager.

"I'm of the age where I remember when her song dropped," she says. "When it came out, I was partying in Scarborough, in basement parties. When they'd put the reggae set on, it was just all men. Then, when her music was dropped, all the women in the party just went nuts.… It meant so much to me."

Duke said that Nancy's only request in making the documentary was that she not have to do anything twice. It's not uncommon for documentarians to ask their subjects to repeat things to capture the moment better. That wasn't going to work for Sister Nancy.

"I asked her to do something, and I think it was something that I wanted to shoot her doing again," says Duke. "And she goes, 'I'm going to tell you something. I'm going to stop you right there. I'm not doing anything twice. You ask me a question, you ask me once. If I'm walking somewhere, I'm only walking once. Don't ask me to repeat stuff. Because if you approach this documentary that way, it's not going to work.'"

Duke says that one-take approach was challenging at times, but it was also a refreshing throwback to the "fly-on-the-wall days" of her early career.

"I really like that energy of just following someone who is just about the moment, and just making a film that's about these moments," she says. "That just sparked some kind of creativity in telling me let's make the movie that way and not try to force it or fight it — but just lean into it."

Bam Bam isn't just a celebration of Sister Nancy's career. It's also a story of Nancy's fight for the rights to her work. Having been sampled over 140 times and counting, Bam Bam is, according to the documentary, the most sampled reggae song of all time and one of the most sampled songs period. It's appeared in movies and advertisements. And yet, Sister Nancy didn't see a dime in royalties for decades. In the Jamaican music industry of the 1980s, it wasn't normal for producers to keep the publishing rights for their stars' songs. In the case of Bam Bam, that producer was Winston Riley, who died in 2012. Nancy's adult daughter encouraged her mother to pursue getting her publishing rights back after hearing Bam Bam in a Reebok commercial, setting off years of legal proceedings. To Duke's surprise, Riley's children agreed to appear in the film.

"I got his kids … to talk about what went down and rectifying the situation," she says. "I thought they were going to shy away from the movie. I thought they wouldn't want to be in it, but they did. They came on board. [Riley's daughter] actually came to the screening in New York at Tribeca, when we had our world premiere there, and she was sitting behind me and I could hear her laughing, yelling at the screen, having a good time. And at the end of the thing, she goes, 'You made a great film.'"

Nancy eventually got 10 years of back royalties, plus royalties going forward. That allowed her to retire from her day job. (Nancy had worked at a bank, in the fraud department, since immigrating to the United States in the 1990s, playing gigs on weekends and vacations.)

Ultimately, Duke said the film is a testament to who Nancy is as a person, and the appeal of her music, which can still rock a party more than 40 years after the fact.

"It [still] sounds fresh," she says. "Anywhere you go and they drop that song, you immediately think where you are is just a cool place to be."