To play actor Felicia Montealegre in Maestro, Carey Mulligan carefully studied any archival material she could get her hands on—including John Gruen’s interview tapes that would go on to be his book The Private World of Leonard Bernstein. The Bernstein family shared their home videos and photos, along with loaning Mulligan some of Montealegre’s clothes and cigarette lighter. And a couple months before filming began, Mulligan traveled to Santiago, Chile, to meet some of Montealegre’s extended family and see where she grew up. “The more we found out, the more we wanted to find out,” says Mulligan of the experience.

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Mulligan’s research pays off—she delivers a commanding performance as Montealegre, whose partnership with the famed composer and conductor (played by Bradley Cooper, who also directs Maestro) is at the center of the film.

But in speaking with Mulligan for Little Gold Men, it becomes obvious that her connection to Montealegre runs deeper than just the in-depth research and the clothing. They have, in many ways, walked similar paths—both being actors who partnered with artists (Mulligan is married to and has three children with Mumford and Sons’ musician Marcus Mumford). “There were things that I kind of understood about her innately, and I felt very comfortable,” she says. And Mulligan reveals that she deeply connected to Montealegre’s resistance to fully committing to acting in some ways, feeling too embarrassed to dive into that vulnerability. But Maestro has changed all of that for Mulligan, who says that, for the first time, she allowed herself to fully immerse into the character—and is forever changed by the experience.

Vanity Fair: Bradley Cooper has said he knew he wanted it to be you to play Leonard Bernstein's wife, Felicia. How did he first reach out to you and what was his pitch?

Carey Mulligan: We sort of know each other a little bit – we bumped into each other at things. He'd seen me in a couple of plays, and so he came to see a play that I was doing in New York, a one woman show called Girls and Boys in 2018. Then we met not long after that, and that’s when he sort of first suggested it, but there was no script or anything – he was making a film about Leonard Bernstein, but also crucially about Felicia, about the two of them, about a marriage. It was clear from the beginning that it wasn't gonna be the “wife to the great man part” that we love to see [laughs].

Where did the research begin for you once you had signed on?

We both realized the dialect was going to be a huge part of it. We had access to these tapes: John Gruen was a writer who spent a summer with him in Italy in ‘67 and he wrote a book called The Private World of Leonard Bernstein. He spent the whole summer interviewing them about every aspect of their lives. There's about two 45-minute long interviews just with Felicia on her own that are really insightful, as much for what she says as for what she doesn't say – the way that she talks about her devotion to Lenny, but also the way that she keeps it all kind of at arm's length in a way that she can walk away from it.

I can't help but notice that you're an actor, she was an actor, and like her, you're married to an artist who is also a musician. What else did you relate to?

There were two things: She had this proximity to someone who could command a huge amount of people. I've stood at the side of stage at Glastonbury and watched Marcus play to a hundred thousand people – it’s something to see that. The most I've played to a theater of about a thousand people, and this is a hundred thousand people singing the words that you've written. I can't imagine what that's like. So there was that standing in the wings that I could relate to and all the feelings that go through your heart and your head when you're watching the person you love doing that.

There's a great bit in the interview where she's talking to Gruen and he says, “what do you do backstage at all of these things?” And she basically implies that lots of women flutter around trying to get his attention and being annoying and she says she basically finds a corner, and then she says, “a great deal of waiting, a great deal of smoking.” I thought, “well, that's familiar” – that sense of this is the most exciting night of someone's month all year that they're coming to see the show, and you've been on tour for a month and you're over it.

And then there was another side of her that was really interesting to me in terms of her work as an actor because she talks in this tape to John Gruen – this is when she sort of given up her career pretty much completely to be his wife and to be a mother to their three children – and he says, “you really should return to acting. You were so good but you never gave yourself a chance.” And she says, “Well, I never gave myself a chance. I was always kind of half in, half out.” She was really, really critical of the acting studio. She thought it was kind of bullshit and kind of ridiculous, and she was much more comfortable with the European approach to theater. She thought the American approach and people writhing around on the floor pretending to be animals was sort of ridiculous. I think part of her probably would have loved to have been able to do that stuff and be part of that community, but she felt kind of on the outside of it because she had such poise and such reserve. There was a part of her that could have really done with just letting go.

When I heard that, I thought, “I know what that is.” I never went to drama school – I didn't get in. I definitely felt there were times when I have watched other actors really committing to something, and I thought, “that’s a bit embarrassing.” But actually, on some level, I've been thinking, “oh, I wish I could do that” because I feel like I’m too English and too embarrassed to actually do all of that stuff – like, keeping my dialect in between takes. Bradley was like, “I really want you to go all in.” And I remember talking to Kim Gillingham, who's my teacher, and she said, “You are allowed to be an artist. What would happen on Maestro if you actually tried?” From that moment, I decided to do all the stuff that I had always been nervous of. And I loved it. It didn't feel weird or embarrassing at all.

Has this changed your approach for future projects?

I think so. It's funny, I did a little job over the summer, two weeks on this little British indie comedy and did none of that. I just waltzed in, had a great time, waltzed off. But I think, largely, that will be the way that I want to. I mean, I did two days playing poor Pamela in Saltburn, and I did not do a dream workshop. I was very much invested in the hair and makeup fittings, but I didn’t research Pamela's back backstory. But I think, probably on the whole, that would be the way that I'd like to work.

How did you and Bradley create the bond between these two characters? I don't even know what a dream workshop is.

Neither did I really. Essentially you record your dreams – wake up in the morning or in the middle of the night and you try and write down your dreams, and then you bring them into the workshop. It's just it was just me and Bradley and then you sort of describe them. And then as you're describing them, you sometimes assign a kind of gesture to one of the things or feelings that happens. It's essentially trying to figure out why your subconscious is bringing that dream to you, and does it connect to the work that you're doing on screen?

It sounds so hippie. There's a lot of soul-baring and a lot of crying, and it just makes you closer. And then at the end of the week, you put on this mini performance art thing, usually to music. I was absolutely terrified to do it because I thought it sounded mad, particularly the last bit where you have to create a little bit of performance art, but it was amazing.