She Knew the Cello. The Acting She Learned With Cate Blanchett.

Lydia Tár commands with the gravitational pull of a planet: Everyone and everything, including the camera in “Tár,” Todd Field’s epic about a fictional maestro, lives in her shadow. But when Lydia (Cate Blanchett), who has been accused of sexual harassment, sets her sights on Olga, a rising Russian cellist, she is confronted with a foil of sorts. Is the young woman disarmingly naïve or particularly cunning?

In reality, Sophie Kauer, who plays Olga, is a British-German cellist who, after responding to a vague open casting call practically on a lark, found herself months later plunked down in front of Blanchett shooting two-hander scenes in Berlin. She was 19 and had never acted in her life.

“Sometimes I feel like everything’s happening backwards,” Kauer, now 21, said recently on a video call from a professor’s classroom at the Norwegian Academy of Music, where she is studying for a classical music performance degree. “I’ve kind of just been dropped into the thick of it, which is both wonderful and so weird at the same time.”

Kauer appeared grateful, dazed and remarkably well-adjusted about the film and the attention. She has been meticulous about scheduling classes around press duties to maintain her school’s mandatory 80 percent attendance rate.

Born in London, she picked up the cello at 8 and has always been naturally driven — she speaks five languages, and for early auditions developed her Russian accent through YouTube videos. (After she was cast, two dialect coaches took over.)

“If I want to do something, then I’ll just do it,” Kauer said, not with arrogance but rather the air of someone who is self-assured about her passions. Music, she emailed after we spoke, “has been my absolute rock through everything. But what I really don’t like is being put in a box and told that classical music is all I am allowed to do or I am not sufficiently serious about my career.”

Kauer spoke about the casting process, working with Blanchett, and what she thinks about that Juilliard scene. These are edited excerpts from our interview.

What has your life been like these past few weeks?

I’m still getting the hang of all of this. Every interview I do is completely different and I learn so much from it. I just think it’s so surreal that someone wants to talk to me. [Laughs]

How did you become involved in the film?

My friend sends me a casting call that has been posted in our school Facebook group, saying, “Look, they’re looking for a young cellist who could do a Russian accent and feels comfortable in front of a camera. I think you should apply for this.” And I was like, “Oh, but I don’t do any acting. I wouldn’t get it.” And she was like, “Oh, just apply. It’ll be fun.”

I wasn’t really thinking about what size the role was. I had a Zoom audition with [Field] and I was like, “This is so cool. I’m going to tell my grandkids that I did a Zoom audition with Todd Field.” Then I got a call asking if I could send a recording of the piece you hear Olga playing in the film, the Elgar Cello Concerto. I had played it before, but I had to get it back in my fingers in like a day and send it straight away. They were really cryptic the week after. It wasn’t until I actually was put on a Zoom call with Avy Kaufman [a casting director] and Todd that I found out I had got the part. No one had actually explained it to me.

Did you have any acting experience?

When the occasional Shakespeare compulsory play came around [in school], I’d play the noble man in the background with the painted-on beard who says “Aye” three times or something like that. [Laughs] That was the extent of it.

Michael Caine did these lessons on film acting [available on YouTube]. That was very technical, but I picked up a lot. I kind of figured it out as I went along. When I would have days or hours off, I asked Todd if I would be allowed to watch everyone else act their scenes. I was trying to pick up everything that they were doing,

What was it like to go from no acting experience to suddenly working opposite Cate Blanchett?

I remember I saw her for the first time she put out her hand and she said, “Hi, I’m Cate.” And you’re just like, “I know!” [Laughs] And then I had to [rehearse with] her after having met her five minutes before.

I quickly learned that she’s one of the world’s loveliest people, and she’s so supportive and generous. I would even go as far to say that I learned to act from her and Todd.

Olga has a very specific dynamic with Lydia. She seems to be the only one Lydia can’t fully control. Why is that?

That’s the thing — you are not meant to know. We have no idea if Olga was just super naïve and very caught up with her life going exactly to plan and her achieving her wildest dreams. Or if she’s super calculating and knows exactly what she’s doing. Part of me would like to think that she’s smart, and the other part of me wants to think that she’s careless and young and kind of free. None of us actually really know the entirety of our characters. I don’t think Todd does either.

What do you make of how the film examines notions of power in the world of classical music?

The release of this film is very timely because the Independent Society of Musicians just released a study saying that sexual harassment, bullying and racism is at its all-time worst in the classical music industry, and that people feel like they can’t speak out about it because they’re freelancers. And when they do speak out, they face repercussions and are not rebooked.

It’s perfect that this film is coming out now. I also think the fact that it’s a woman in a position that a man would stereotypically be in is really good, and in a way is slightly less offensive. People kind of just see the problem for what it is, rather than getting offended.

The film has been discussed at length within the framework of the culture wars, in particular with the scene at Juilliard when a student expresses discomfort playing music written by straight white men. Lydia has no patience for him. As someone in these classrooms, do you have sympathies for either side in that Juilliard scene?

Of course I do. We need to be open to discussing it and including all these new voices that have been unheard for so long — music by women or including more cultures and ethnicities. And we can’t just forget what has gone before because this is what our whole history is based on. I can’t wake up tomorrow and say, sorry, I’m never going to play a piece written by a white male composer again. Because unfortunately that is just how history is, and that is the vast majority of our music.

You can’t exclude the majority of music history because you don’t identify with it. But I also do think that the point he makes is very relevant. There is very little representation for a lot of genders and ethnicities and cultures, and classical music may have been a bit slower to evolve. But it is evolving. Every time I watch, my sympathy for each character changes. Sometimes I think Lydia is totally right, and other times I’m like, no, Max, he’s the one who’s totally right.

What’s next for you?

I am still in the middle of studying for my music degree, so I have a lot of stuff to catch up on. I’m looking forward to being a musician again. But I did enjoy the acting a lot. I’m still very young, so I’m kind of seeing what happens and taking it one thing at a time. I would like to hope that this isn’t my last project. It was really quite something.