'The Testament of Ann Lee': Go behind the scenes of Amanda Seyfried's new film

LOS ANGELES -- It's one of the most unconventional and unique films of the year. Now, On The Red Carpet and Searchlight Pictures have teamed up to take viewers behind the scenes of "The Testament of Ann Lee."

The film stars Amanda Seyfried as the charismatic Ann Lee, who becomes the leader of the Shaker movement in the late 1700s.

Director Mona Fastvold wanted to make sure the look and feel of the film, from the sets to the wardrobe to hair and makeup, was accurate for the time period and to the Shakers. And everyone went all in on her vision.

"Every department was locked in," said Seyfried. "And I think it's because everybody understood this was a once in a lifetime opportunity."

Fasfvold added, "Filmmaking is a collaborative art form. We were a really tight knit group."

The Shakers lived their lives through song and dance and they're known for their hymns and those songs are what helped create the film's soundtrack.

"We decided that we wanted to dive into the musical history of the Shakers and start listening to all of their songs and their hymns and just see sort if we could find things that felt like it belonged in our film," said Fastvold.

Part musical, part biopic, part drama, both Seyfried and Fastvold were happy to immerse themselves in this world.

"Obviously we didn't become Shakers," Fastvold said.

"Yet," Seyfried added. "This experience is not taken for granted either, because I would hope that I can come back to [the] film set and have some kind of feeling of this kind of utopia that we had, because in a lot of ways it was the best version of a film set."

Watch the "On The Red Carpet Presents: The Testament of Ann Lee" special in the player above.

"The Testament of Ann Lee" is playing in theaters everywhere.

The Walt Disney Company is the parent company of Searchlight Pictures and this ABC station.