As a planned release date approached in 2011, however, Ms. Franklin sued Mr. Elliott for using her likeness without her permission. That started years of legal wrangling, with Ms. Franklin and her lawyers blocking Mr. Elliott and the Telluride Film Festival from showing “Amazing Grace” in 2015 and 2016, even after deals for her compensation seemed to have been worked out. The singer’s opposition appeared not to have anything to do with the film’s content, which she had said publicly that she “loved.”

“There is just this deep-seated desire for something to not happen right now, so I’d rather just respect her wishes,” Julie Huntsinger, executive director of the Telluride Film Festival, told Variety last year.

Film insiders speculated that the release of the movie, which ends with a young Ms. Franklin performing “Never Grow Old,” was simply too difficult for the ailing singer to confront — that she knew it amounted to a eulogy.

Legal clearance finally came after Ms. Owens invited Mr. Elliott to her aunt’s funeral in Detroit. A couple of weeks later, he contacted Ms. Owens about restarting talks. “Sabrina said, ‘Why don’t you come and show the movie to the family?’” he said. He flew to Michigan and did just that on Sept. 20. About 25 people were there.

“There was clapping and crying,” Ms. Owens said.

Mr. Elliott said that he spoke to Ms. Owens as he left for the airport and she said, “Let’s do it.”

Unless “Amazing Grace” hits an unforeseen snag, its release will mark the second time this year that a film will have made its way to theaters after decades in purgatory. “The Other Side of the Wind,” which Orson Welles left unfinished upon his death in 1985, was completed and shown for the first time in North America at the Telluride festival in September. Netflix started streaming it last week.

Moviegoer interest in “Amazing Grace” will most likely be strong. Feel-good documentaries such as “Won’t You Be My Neighbor?,” about Fred Rogers, the star of public television’s “Mister Rogers’ Neighborhood,” and “RBG,” which looks at Ruth Bader Ginsburg, the Supreme Court associate justice, have lately been ticket-selling machines. Movies built around music have also been doing well with audiences. Over the weekend, the Freddie Mercury biopic “Bohemian Rhapsody” arrived to an astounding $50 million in ticket sales in North America.