Music annals tell us about legendary lost projects that got released long after the fact. The Beach Boys’ “Smile.” Bob Dylan’s “Basement Tapes.” Prince’s “Black Album.”

Now comes the holy grail: “Amazing Grace,” the movie of Aretha Franklin’s storied gospel concerts in 1972. For two nights in a Baptist church in Los Angeles, the queen of soul revisited her gospel roots.

The two-disc LP of the concerts is the biggest-selling live gospel album in history. Those concerts were also filmed, but the crew made a crucial production error. With the technology of the day, it was impossible to sync the sound with the visuals. Even decades later, when digital technology finally enabled the film to be finished, Franklin blocked it from being shown.

“I love the film itself. It’s just that, well, legally, I really should just not talk about it, because there are problems,” she said in 2015.

Franklin’s death last year opened the door for the release of the film, which has the approval of her estate.

You don’t need to be a churchgoer to find “Amazing Grace” a soul-stirring experience. When you hear Franklin magnificently turn one syllable into five, you’ll be moved to hand-clapping ecstasy just as Mick Jagger was when he joined the congregation on one of those nights.

You’ll realize how deep Franklin’s gospel roots extend. You hear her father, the Rev. C.L. Franklin, talk about his daughter, at age 11, singing with him as a traveling preacher. The Rev. James Cleveland, Franklin’s mentor and a gospel star in his own right, praises her ability to sing anything, including “Three Blind Mice.”

With Cleveland presiding and playing piano, Franklin interprets material from the Great Gospel Songbook. “Climbing Higher Mountains,” “Mary Don’t You Weep,” Clara Ward’s “How I Got Over,” Marvin Gaye’s “Wholly Holy.”

When she gets to “Precious Memories,” she slowly testifies from deep in her soul. And then she does it again.

There are other special moments in the film, including when Rev. Franklin walks up to his daughter in mid-song and wipes the sweat off her face with his hankie. And when she mashes up “Precious Lord Take My Hand” with Carole King’s “You’ve Got a Friend.” And when she Aretha-izes “Never Grow Old” with the intense, liberating emotions of her voice expressing more than mere words could.

“AMAZING GRACE”

*** 1/2

(G, 1:29)