COLUMBIA, Md. — The soprano Leontyne Price, who retired from singing 20 years ago, assumed that the triumphs of her illustrious career were behind her. Not so. At 90, Ms. Price has become an unlikely movie star.

She may not quite be in line for a spot on the Hollywood Walk of Fame. But again and again, Ms. Price steals Susan Froemke’s new documentary, “The Opera House,” which tells the complex, tense saga of the building and inauguration, in 1966, of the Metropolitan Opera House at Lincoln Center.

The “New Met” opened with the lavish premiere of Samuel Barber’s “Antony and Cleopatra,” tailored to Ms. Price’s radiant voice and prima donna grandeur. And she dominates the documentary, both in footage from the ’60s and in interview segments filmed just before her 90th birthday, in which Ms. Price recounts the opening night with impressive detail and droll humor, along with charming (and amply justified) self-regard.