Amanda Seyfried tackled a tall task by stepping into the shoes and strict religious beliefs of Shakers founder Ann Lee for her new film, The Testament of Ann Lee, which is not quite a musical nor a straightforward biopic. The film’s writer and co-director Mona Fastvold fielded an obvious question during today’s Venice Film Festival press conference: Why Amanda?

“Amanda has a lot of power. She’s really strong. She is a wonderful mother. She is a little mad,” Fastvold explained of her Emmy Award-winning and Oscar-nominated star. “So, I knew that she could access those things, the kindness, the gentleness, the tenderness. And she could also access this power and this madness.”

The actress toplines the Venice selection directed by Fastvold from a script the filmmaker co-wrote with her The Brutalist partner Brady Corbet. It casts Seyfried opposite Thomasin McKenzie, Lewis Pullman, Stacy Martin, Tim Blake Nelson, Christopher Abbott, Matthew Beard, Scott Handy, Jamie Bogyo, Viola Prettejohn and David Cale, with music by the Oscar-winning Daniel Blumberg, also from Corbet’s monumental work The Brutalist.

In the film, described as a “speculative retelling,” Seyfried stars as the founder of the radical religious sect the Shakers. The cult-like group, which formed as an offshoot of Quakerism in Manchester, England, in 1747, got its name from worship practices that included trembling, dancing and speaking in tongues. Lee espoused gender and social equality while believing herself to be the female incarnation of Christ, and the group’s members practiced celibacy and communal living. The Shakers ended up fleeing to America to escape persecution, ultimately settling near Albany, New York, to build their utopia.

In Fastvold’s film, more than a dozen original Shaker hymns are transformed into ecstatic “movements” with choreography from Celia Rowlson-Hall, who worked with Corbet on Vox Lux. Fastvold said the Shakers’ catalog includes close to 1,000 hymns and they “found the ones that felt like they belonged” in the story, adding that it was a beautiful and exciting process to access this “rich history” of music. But don’t think of it as a straightforward song and dance pic because no one is actually singing dialogue.

“It’s not a traditional musical and it’s not a traditional biopic,” Fastvold explained. “It’s a film with a ton of music, a ton of movement, and it’s about a historical figure, but we don’t really know that much about her, really. I really had to rethink what this could be for myself. And it was hard to look at any other musical as a reference, honestly, because I couldn’t really find anything that quite spoke to this.”

Without any references and with a supportive director, Seyfried said she felt game to go completely free.

“This did feel like an opportunity where there were just no tethers to anything,” the actress said at the press conference. “Basically, I follow Mona into the light and anything goes because there’s so much freedom, and the only threat is to not use that freedom to your advantage as an artist to go as far deep as you can go to make the craziest sounds. I’ve never been let loose in this way.”

Even still, Seyfried admitted that she told Fastvold, “You don’t have to cast me.”

“I kept saying, ‘Go with somebody English,’ because the accent seemed so hard. That wasn’t the hardest part,” added Seyfried, who had tackled tough parts like those of Cosette in Les Misérables and Elizabeth Holmes in The Dropout. “But it was just, I saw the love Mona had. This was her baby, and I didn’t want to f- it up. But she believed in me, and so I believed in me, and here we are.”

Another journalist asked Seyfried how she managed to pull off what is an “intense and physically challenging” role that requires lots of vocal energy and unique sounds. “There are so many things I can say,” Seyfried noted before praising Fastvold and the community she created on set that was not unlike what the Shakers experienced. “The reason I was able to face these challenges as an artist, which there were many as you say, was because I felt completely protected, held up and surrounded by loving artists, and in a place where everybody knew the value of making this, and understood Mona’s vision. It’s just very rare. I have to say it this was incredibly rare and might never happen again.”

It sounded like a singular experience for many involved. “One of the great things for me was being able to work with Mona through the whole process, starting with preproduction on the set even up to the sound mix,” Blumberg explained at one point during the presser. “It’s one of the most experimental, extreme project I’ve ever done. But we were able to try things and use our instincts.”

The press conference panel featured Fastvold, Corbet, Seyfried, Blumberg, producer Andrew Morrison and choreographer Rowlson-Hall. At one point, Corbet gave a shout-out to Morrison for being able to get the movie made for “$10 million bucks,” which he said was quite a feat. “As you can imagine, the elevator pitch for a Shaker musical was not the easiest thing to get off the ground.” Corbet, who handled second unit directing on the film, also noted that he and his romantic and professional partner insist on the final cut for their projects.

In her festival director’s statement, Fastvold confirmed that while she was raised in a secular household, Lee’s prophecies, “however implausible,” moved her deeply. “Not because I share her faith, but because I recognize in her a yearning for justice, transcendence and communal grace. Her radical pursuit of a self-fashioned utopia speaks to the creative impulse at the heart of all artistic endeavor: the urgent need to shape the world anew.”

She said her film is offered as a tribute to Lee’s dream “and the silence that now surrounds it.” The Testament of Ann Lee has its world premiere Monday afternoon inside Sala Grande. The Venice Film Festival runs Aug. 27-Sept. 6.