It’s almost surprising that Jethro Tull’s “Living in the Past” isn’t included in the soundtrack of “Gloria Bell” – so much of the film deals with living in the past and acknowledging issues that have lingered for years.

Then again, the disco-nostalgia soundscape of “Gloria Bell” doesn’t have room for anything that its title character can’t dance to. Gloria (Julianne Moore) loves the nightlife and loves to boogie, and she escapes regularly to Los Angeles nightclubs that cater to that clientele.

Divorced and in her 50s, Gloria exists in a state of seemingly happy semi-detachment. She works as an insurance agent and seems warm and caring, but her job doesn’t mean much to her. She isn’t in a romantic relationship, so she reaches out to her grown children, who love her but don’t have a lot of time for her.

She meets Arnold (John Turturro) while dancing, and they hit it off. He’s kind of witty and is definitely interested in her. Gloria takes a why-not approach to seeing Arnold, but she quickly grows fond of him.

“Gloria Bell” is not a romance but a snapshot of life – the life of a woman of a certain age, in a certain demographic, in a certain socioeconomic sphere. It’s almost tailor-made for an audience that is often overlooked. Sometimes that is more blatant than others.

What raises it above a concept is its unpredictability. Some plot turns are expected, but most are not. And since Moore is at the heart of it all, it’s hard to be cynical.

It’s funny to think of the sidekick Moore played in “The Hand That Rocks the Cradle” – how she was singled out as a star way back then (in 1992) – and look at how she has delivered in her career. She has portrayed a variety of characters and has succeeded at making nearly every one unforgettable. She takes the best traits of her predecessors – one thinks of Katharine Hepburn, Meryl Streep and Diane Keaton – and melds them into an essence that’s unique but not routine.

As Gloria, she’s a treat – a mom who’s never been to one of her yoga-teacher daughter’s classes; a grandmother who seems to have forgotten what it’s like to be around babies; a loyal friend who flees the scene or shows up late for a wedding. Gloria’s world revolves around her, but she’s not sure what’s at the center of it.

Meanwhile, the rest of the cast rises to Moore’s challenge. Turturro, so often the smart and snarky one, is amazing as Arnold, who starts out robust but gradually peels off layers of insecurity and ineffectiveness. Michael Cera is touching as son Peter, while Caren Pistorius gives daughter Anne the strength, intelligence and warmth one would expect from a veteran actor.

The cast is full of familiar faces that make Gloria’s world an instantly friendly place: Holland Taylor, Barbara Sukowa, Rita Wilson, Jeanne Tripplehorn, Chris Mulkey, Sean Astin and Brad Garrett (at his most appealing). Nearly all of their characters are interesting enough to warrant at least a short story. (Hear that, screenwriter Anna Johnson Boher?)

Chilean director Sebastian Lelio obviously loves spinning this yarn – and spinning, in general. It’s a metaphor for the Earth turning, possibly, but also for the constant rotation in Gloria’s life as she opens herself to change. Which brings up another oldie but goodie, “Turn, Turn, Turn” – but neither Bob Dylan nor the Byrds would fit in this synth-heavy feast.

“Gloria Bell” is rated R for sexuality, nudity, language and some drug use.