Three major Israeli actors at the top of their game explore the dark secrets crippling a long-term marriage in “Karaoke,” a powerfully spare film of jealousy, repressed desire and the need for acceptance.

Following its world premiere in June at the Tribeca Film Festival, “Karaoke” is the San Francisco Jewish Film Festival’s opening night selection, and one of the stars, Lior Ashkenazi, is expected to attend that July 21 screening at the Castro Theatre.

The film is billed as a comedy-drama, but the humor appears intermittently, and often serves to impress upon the audience how tone-deaf the characters can be to their own foibles.

Sasson Gabay (“The Band’s Visit”) has never put his remarkably tragic visage to better use than in his portrayal of Meir, a man so numbed by his own mediocrity that he doesn’t have the energy to change his facial expression. Our first view of him is a closeup as he stares out at the night skyline from his balcony, his expression impassive and unreadable.

Disparaged as uninteresting by Tova, his wife of 46 years (played by the iridescent Rita Shukrun), his feeble effort to tell a story at the dinner table ends, as we are led to believe all such attempts do, in utter failure.

Clearly this couple needs a spark in their marriage, and it comes in the form of Itzik, a worldly and charming man who moves into the penthouse of their apartment building in Holon, a nondescript Tel Aviv suburb whose very name is a middle-class Sephardic stereotype in Israel. Played by the magnetic Ashkenazi (“Footnote,” “Walk on Water”), Itzik shakes them out of their somnolence with his zest, his constant parties and his disarming ability to ask very personal questions that push the couple to reveal parts of themselves they have long kept hidden.

From the first moments of their initial meeting, after he has invited them “for wine and music,” it is clear both Tova and Meir are entranced by this charismatic man. He seems to be deeply interested in each of them, and they flower in his presence. Tova beams as he asks her to sing karaoke for him, and Meir can’t stop grinning when Itzik takes him on a nighttime motorcycle ride (and invites the hapless man to hold onto him).

Yes, he seduces them, in every sense. An intense sexuality colors all their encounters, from Itzik’s first question to the couple — “46 years? And are you monogamous?” — to Meir dying his hair and Tova wearing her long-neglected stilettos, prompting their adult daughters to collapse in laughter. “You are ridiculous!” one of them shouts.

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But is Itzik real? Why is he interested in these two sad sacks, whose idea of fun is a yearly trip to the Greek island of Rhodes, where they always stay in the same hotel? How far will they go in their attempts to win his approval, his love?

Virtually the entire film takes place at night, with scenes shot in near-darkness. Itzik’s apartment, however, is bathed in a strange blue light — so much more interesting than white, he tells Meir and Tova — that gives his home, and him, the air of a dream. As he slowly, almost methodically breaks them open, will he take the care to put them back together again?

Despite its name, “Karaoke” is a very quiet film. Dialogue is sparse, with many long takes shot in silence. The actors’ faces are all that is needed to convey their growing confusion, jealousy and self-recrimination, along with the joy Itzik awakens within them — a joy that is all the more touching because they have had so little.

This is a compelling and thoroughly engaging film about the strength and fragility of human relationships, one that constantly surprises while building to a powerful conclusion.

“Karaoke” (103 minutes, in Hebrew with English subtitles) screens at 6:30 p.m. Thursday, July 21 at Castro Theatre, 429 Castro St., S.F. After-party at nearby Randall Museum, 199 Museum Way, S.F. $35 general, $30 members for screening only, $75/$65 includes party.