A two hour and thirty-eight minute deep dive into the life and downfall of an exacting, mercurial lesbian classical music conductor might be the motion picture definition of “a hard sell.”

But you miss “Tár” at your own peril.

Consider what Cate Blanchett does in creating and presenting the title character, Lydia Tár, conductor of the Berlin Philharmonic whose classical music career has dashed through permanent positions and guest-conducting gigs at most of her profession’s greatest ensembles, including America’s “Big Five” — The Cleveland Orchestra, Philadelphia Orchestra, New York Philharmonic, Chicago Symphony and Boston Symphony.

Blanchett’s Lydia is brittle, brilliant and considered in every public moment. It is a self-aware performance of a performance. We see her get her “game face” on in the rare less guarded moment. But to everyone from her long-suffering assistant (Noémie Merlant) to her symphony board, her mentor (Julian Glover, ancient and in fine form), her musicians to her wife (Nina Hoss), she is “Tár,” a woman of accomplishment and self-confidence, all-controlling and all-knowing. If she wants to be considered more than “a gender spectacle” in the ancient and austere boy’s club that is orchestral conducting and music directing, she has to be.

It’s all put on peacocking display in the opening scene of writer-director Todd Field’s (“Little Children,” “In the Bedroom”) study of a powerful character put under duress. It’s one of those New Yorker-sponsored “An Evening With” chats, and Lydia hops from English to phrases in German, French and Italian with fluent ease, swooning over her “inspiration,” “Lenny” (legendary New York Philharmonic conductor and TV educator Leonard Bernstein) and dissecting the works of their shared orchestral passion, Gustav Mahler.

She’s about to finish recording a complete cycle of Mahler symphonies with “The Five,” as his fifth symphony is insider-labeled here. She has a memoir, “Tár on Tár,” coming out. She teaches conducting at Julliard when she isn’t at home in Berlin, with her wife — who is first chair violin with the Berlin Philharmonic — and their little girl, Petra.

And the person who makes all this work is her musician and aspiring conductor assistant, Francesca (Merlant), who might be the source of the faintly-snippy candid photo-and-video texts we see from time to time. The impatient, imperious Lydia may have a few friends — Mark Strong plays a conductor and colleague who helps with her foundation. But Francesca is who lets Tár be Tár.

Lydia is ready to dump her older, fussier associate conductor (Allan Corduner). She continues to bend, shape and hire this pinnacle of orchestral music to her will. But German law gives her players a lot more power in their relationship than is common elsewhere. And there’s something bubbling below the surface, something unpleasant whose nature we can easily discern and whose direction any movie-lover can guess. Lydia Tár is about to “go through some things” as we say these days.

“Tár” doesn’t set out to be a movie for everyone. But if you’re into classical music and know even just a little about this world, it is a film to be savored and treasured. The banter — touchy negotiations with “DG” (classical music label Deutsche Grammaphon records) over whether they’ll record this Mahler symphony “direct to (vinyl) disc,” discussions of “musical grammar” and “atonal tension” and snippy remarks about this famous name or that one (a dig at conducting rival “MTT,” Michael Tilson Thomas, another Follower of Lenny), discussions of “signal to noise ratio” — sparkles and immerses.

We hear snippets of an appearance on Alec Baldwin’s podcast, lots of NPR and hear and see Tár in action with her Julliard students and endless scenes of her working and rehearsing her orchestra. Blanchett is so animated, exacting and convincing I dare say she could fake her way to any podium on Earth after this.

Lydia composes and makes notations on scores while at the piano, her keener-than-keen ears relishing silence but absent-mindedly matching the tones of a doorbell on the keys.

The milieu is complete, three-dimensional and so spot-on we’re ensconced in it with her.

The viewer notes that violinist-wife Sharon is highly strung and medicated, that little daughter Petra (Mila Bogojevic) calls her parents by their first names. And then we see Lydia take her to school and have a word with another seven year-old girl who is bullying her daughter.

In perfect German, she tells the child “I am Petra’s father.” And then she gives the mean girl the most cold-blooded threat you can imagine.

If we haven’t guessed before now, before her dismemberment of a Julliard student too “woke” for her tastes, we figure it out here. Lydia Tár destroys people.

“Tár” is, as mentioned, quite long for a story as compact as this one. Field almost drowns us in details — Lydia’s visit to her tailor, Lydia looking over hundreds of other classical music album covers before deciding how to pose for hers.

At times I wondered if Field was leaning into “U-Haul Lesbian” stereotyping a tad too hard — chilly parenting, bitchy callousness, “re-invention,” infidelity, that Diane Keaton-meets-Ellen wardrobe.

But Field and Blanchett have given us an unforgettable character presented in almost molecular detail, and a glorious, guts-and-Gustav behind-the-scenes plunge into a rarefied world few of us have so much as dabbled in or seriously wondered about, even if we know our Tchaikovsky from our Mahler, pianissimo from forte.

Rating: R for some language and brief nudity

Cast: Cate Blanchett, Nina Hoss, Noémie Merlant, Julian Glover, Sophie Kauer and Mark Strong.

Credits: Scripted and directed by Todd Field. A Focus Features release.

Running time: 2:38