How Angelina Jolie recorded her raw vocals for “Maria.”

“I’ll sing when I’m ready to sing.”

That’s a line from Pablo Larrain’s “Maria,” now streaming on Netflix and based on the final days of opera superstar Maria Callas. The film is peppered with flashbacks to arias by Verdi and Puccini, when Callas was at the height of her success.

And was Angelina Jolie, who plays Callas, ready to sing it? Absolutely not.

She may be a trained actress – as a young teenager she took acting classes at the Lee Strasberg Theater Institute – but she is not a trained singer.

In order for Larrain to make the film with Jolie as the lead, he knew one thing: he wanted that performance to be believable. Larrain says, “It’s opera, you can’t cheat.” That meant Jolie wouldn’t be lip-synching through her performance.

To play one of the most famous sopranos in the world, Jolie underwent rigorous preparation and went through all the necessary steps to make it happen. Jolie went into her first singing class saying she was “deaf.”

Larrain notes that she spent over a month practicing each aria she had to sing. But it required much more from the actor.

Summing up her process, Jolie says: “We trained for seven months. We started with breath work, posture and finally went back to the basics of sound.” She continues: “We just learned Italian for a few months. An opera singer came in so I could sing with her and understand the difference.”

When the cameras rolled, “Ave Maria” was one of the first scenes they shot. Jolie remembers being “scared.” I was extremely nervous and extremely insecure.” It was a moment of reckoning for her. While Larrain had limited the number of crew members present on the scene to those who needed to be there, Jolie had doubts. “Have I worked enough? Am I sufficiently prepared? Can I sing enough?” She continues: “Will John (Warhurst), the film’s sound engineer, look over at Pablo and say, ‘This is a mess?'”

The singing and performances were recorded live. “It’s not just about giving a performance where you stand on stage and sing the song. You sing it 20 times,” explains Warhurst. “The reason we do this is because it gives us a lot of great footage.”

In some scenes, Jolie’s Callas performs with a piano, in others, when Callas is at the height of her success, there is a full orchestra. Capturing those moments behind the scenes was a different story.

Jolie reveals: “To really mix us properly, I had to be the only sound in the room, so there could be no piano, no Maria, nothing.” She adds: “The only sound in the room was my voice, those were just that the most frightening news.”

But the process meant every breath and sound was recorded.

Jolie’s live singing also provided the team with an important piece of the puzzle. “We also get the visual performance that we need to work on with the image editor to accurately frame the image so that the image makes sense musically,” says Warhurst.

Next, Callas’ vocals were extracted from the recordings. Even before that, the next step was to make Jolie’s performance sound as close to Callas as possible. Warhurst explains: “We achieved this by using EQ changes and tonal qualities to suit Maria.”

The audio mix was all about percentages and paying attention to every word and line, with Callas’ voice, especially in her prime moments, setting the tone.

However, there are moments when the proportion of Jolie’s voice dominates. Warhurst says: “If we use a bit more of Angelina there then that will be really cool. And then we really believe it.”

During a performance of Anna Bolena at La Scala, Jolie’s Callas completely collapses and her housemaid Bruna (Alba Rohrwacher) records the performance so she can hear what she sounds like. “It’s almost all Angelina,” says Warhurst. “That’s how she performed it that day and it was just perfect. We just thought, ‘We’ll just use this.'”

Jolie remembers filming this scene. The stage was available for four hours. “They got it towards the end, so we worked towards that. It’s like the greatest memory I have. I’ve never been more scared, never more insecure and never felt smaller.” She adds: “We were all very nervous the day we did it.”

Jolie also learned that she couldn’t see the conductor because Larrain and cameraman Edward Lachman would be taking 360-degree shots. “It was so over the top for me,” Jolie recalls. “During rehearsals in the dressing room I wasn’t shy because I felt like I didn’t deserve to be in the dressing room at La Scala. The whole thing was simply overwhelming. But sometimes I say to Pablo, “It’s great that it was this crazy scene because the emotions were so big that day.”

The months of preparation and vocal, breathing and posture training worked. Jolie is absolute perfection and delivers a performance that Callas would be proud of. Larrain says: “That’s why you feel like she’s actually singing, because she’s doing it.” He proudly adds: “She did it. I was there.”