The documentary “Ailey,” opening nationwide in theaters Aug. 6, is a long-overdue portrait of the modern dance pioneer.

Alvin Ailey died in 1989 at age 58, but, significantly, much of the Insignia Films documentary was filmed in 2018 at a New York dance studio near a street named Alvin Ailey Place. As we watch a new generation of Ailey dancers taking direction from hip-hop choreographer Rennie Harris, it’s as though Ailey never really left; he and his company have always evolved to meet the times.

At the time, Harris had been commissioned “out of the blue” by Robert Battle, artistic director of the Alvin Ailey American Dance Theater, to create a work about Ailey for the 60th anniversary of the company, founded in 1958. We see him focusing intently in a screening room, watching and re-watching archival footage of Ailey, as he worked to create what would become “Lazarus.”

“I just sit there and watch,” Harris says, “to find out what made Mr. Ailey Mr. Ailey.”

What did make Mr. Ailey Mr. Ailey? The director Jamila Wignot grapples with this question, too, in this compelling film about the legendary dancer, director and choreographer — the one who brought Black culture into the dance mainstream. The documentary premiered in January at the Sundance Film Festival.

Given Ailey’s stature and enduring impact, and given that he died more than three decades ago, it’s a wonder that the question is still being asked. The Ailey company has performed on six continents for millions of people. Ailey’s masterful 1960 ballet “Revelations,” which draws on the sorrows and jubilation of African American spirituals, gospel and blues from the “blood memories” of his Texas childhood, is considered a cultural treasure. It’s been said to be the most widely seen modern dance work in the world.

“They wouldn’t let us off the stage,” former Ailey dancer Hope Clarke recalls in the film, describing a performance in Europe. “It was about 80-some bows that we had to do. I’ve never seen people stand up and take their shoes off and hit the wall! No matter what we did, those people would not go home.”

But Ailey’s artistic legacy is more than the sum of the dances he created, searing though they are. It derived from his early years during the Depression, growing up Black in small-town Texas without a father, picking cotton with his mother when he was just 4 years old, sometimes going hungry.

“I mean, if you were Black, you were nothing,” Ailey says in a segment of a rarely heard audio interview with journalist A. Peter Bailey that was recorded over 20 hours shortly before the choreographer died. “I remember seeing my mother on her knees scrubbing these White folks’ rooms and homes.”

Listening to his recollections, paired with moody and evocative archival footage of the Deep South, it’s clear that Ailey was destined to dance. It’s as though dance moves unfolded from his DNA. When he describes his rural childhood, it’s in terms of movement and the placement of bodies in space. He speaks of “people moving in the twilight,” “being glued to my mother’s hip, sloshing through the terrain, branches slashing against a child’s body . . . looking for a place to be.”

When Ailey was 12, his mother moved to Los Angeles to work in the aircraft industry and sent for him a few months later. As a teenager, he was drawn to dance and theater, although he never saw Black dancers or actors onstage — “nobody to model yourself after.” Until he was 15, that is, and Katherine Dunham’s company came to town. Ailey was gobsmacked.

“I couldn’t believe there were Black people on the legitimate stage,” he says. “I was just taken into another realm.”

And he remained in this realm until he died, sacrificing everything to dance, embracing a mission that was revolutionary for his time. Ailey created a racially diverse company with all body types to celebrate, honor and reflect Black traditions and experiences. He very consciously created dance not for the elite, but for “the man in the street.”

“Choreography was his catharsis,” says Sarita Allen, a former Ailey dancer and one of more than a dozen dancers, directors and choreographers who shared stories about Ailey, including Judith Jamison, chosen by Ailey as his successor before he died; Battle, who took over in 2011; and guest choreographer Bill T. Jones.

Ailey’s work also was lonely and exhausting, occasionally leading him to dark and destructive places. He let few people in — literally. Even close friends never saw the inside of his apartment.

Although not a dancer herself, Wignot, the film’s director, is “a huge Ailey fan” who first saw the company perform when she was a college student in Boston in the 1990s. So when Stephen Ives and Amanda Pollak of Insignia Films approached her about directing a film about Ailey’s life, she jumped at the opportunity.

At first, Wignot says, making a film about Ailey was just an idea, with a lot of unknowns: How much of him could be in the film? What material would be available to her? Who would tell the story? Most critically, how could she tell the story through Ailey’s eyes?

“I wanted to know where this work emerged from, what experiences affected him,” she says. “I wanted to know what was feeding him, as an artist, and a person.”

Given the enduring and kinetic nature of Ailey’s work, the film called out for a contemporary element. “It needed to be a living, breathing entity,” Wignot says. “Ailey was sensitive and vulnerable but very alive to the world.”

In a “moment of serendipity,” she says, when they first approached the company, Battle told them they’d just commissioned the Harris work. “Ailey” intercuts footage of rehearsals for “Lazarus,” which addresses racial inequities Ailey faced throughout his life.

“I think the film really resonates today,” Battle says. “We see some of the same conditions today, in terms of the racial upheaval, the bigotry, the hate, the injustice that in a way was the starting point for him wanting to have a company in the first place.

“The arts are the artifacts of human survival. And so this film offers us another point of view — that if [Ailey] could do it, then why can’t I? We can’t all be Alvin Ailey, but we can tell our story. We should tell our story, knowing we could liberate someone else.”