In the documentary “The Sit-In: Harry Belafonte Hosts the Tonight Show,” producers Valerie Thomas and Joan Walsh and director Yoruba Richen aimed to bring back home a seminal event in television history whose themes still resonate.

It was 1968, war was raging and racial tensions in America were at a boiling point, dividing the nation. In February, Harry Belafonte stepped in for Johnny Carson to host “The Tonight Show.” It was a monumental moment in which an African American would be the frontman of the most dominant program in late night — and perhaps all of TV — for an entire week. Guests included Lena Horne, Paul Newman, Aretha Franklin, Martin Luther King Jr. and Robert F. Kennedy.

The doc was scheduled to screen in April at the Tribeca Film Festival, not far from where “The Tonight Show” was filmed in the ’60s, with an after-film discussion that was to have included Belafonte’s daughter, Gina. “We were so excited,” says Richen. “It’s a New York story, and I’m a New Yorker.”

But as with many eagerly anticipated independent films this year, the movie’s launchpad disappeared when the festival was canceled due to the coronavirus, making it a work about the events of yesterday informing today — trumped by the health crisis of the moment.

Richen (gay rights doc “The New Black”) first considered how best to tell the story. Among the biggest challenges she confronted was a lack of footage. As the film describes, NBC typically recorded over episodes of “The Tonight Show.” The only two installments of the programs Belafonte hosted that remained were the ones that included Kennedy and King.

But there was a common thread with Belafonte’s guests that week: Sidney Poitier and all the others were political. Dionne Warwick was a guest on the show along with a young Franklin; both had donated money to the civil rights movement, a cause that was near and dear to Belafonte. The team decided to lean even more into the bigger picture. 

“We focused on the events of 1968,” Thomas says. “We focused on all that Harry had done, and we focused on the shift of politics within the realm of late-night television.”

The filmmakers worked hard to track down guests who were still alive, says Walsh. Franklin died just before shooting began, but they reached out to Petula Clark, Warwick and, particularly, to Belafonte. 

Walsh, a national affairs correspondent for The Nation, wrote an essay about the week of shows and told Belafonte about it. “His story about late night was hiding in plain sight. It was in his memoirs, ‘My Song: A Memoir of Art, Race, and Defiance.’ I was obsessed with it,” she says. Adds Thomas: “We got early access to Harry. We told him our vision, and we did two interviews with him.” Everyone else they asked to participate said yes.

Mixing the new material, audiotapes and existing footage of the guests reveals the story of the times. But the way the production had to be completed is a tale more familiar to current events.  

Thomas was putting the finishing touches on the documentary when the pandemic forced a shutdown. Homes became offices for editing, visual effects and sound mixing. “Big Beach Films [‘The Farewell,’ ‘Little Miss Sunshine’], which helped finance the documentary, had created a plan of who needed to bring home what and what could be done,” she says. “Everyone did their job. It’s a case study in what you can do remotely.” (Big Beach says it is actively selling “The Sit-In” to distributors.) 

Among those working from home were editor Èlia Gasull Balada, co-editor Joe Borruso, assistant editor Ha Vo and composer Wendell Hanes. Says Hanes: “I created most of the sonic layerings in my home studio and used Zoom to communicate with the band.”  

Ultimately, key moments in the documentary reveal Belafonte’s intention to use the week to introduce ideas of social change to a mass audience. “In the television footage, you see the interactions,” Thomas says. “There are laughter and jokes [with King and Kennedy] but you see their concern and what they were really thinking” — their vision for integration. 

Both were assassinated a few months later.

Richen says that working on the project helped her better understand Belafonte. “I didn’t know the depth of his activism and his work in the [civil rights] movement,” she says. “I didn’t know about his connection to the people.” She says that despite the production and exhibition setbacks, “The Sit-In” delivers what it set out to do. 

“It says a lot about the politics of today and where we are,” she says. “And that late night is still dominated by white men.”