Lauren Patten is a showstopper you oughta get to know

It started during the first preview performance of “Jagged Little Pill.”

In the middle of the second act, right after Lauren Patten, 25, performed “You Oughta Know,” the American Repertory Theater audience began to stand, and then stayed on its feet, cheering in the actress’s direction, for the better part of a minute.

Director Diane Paulus said the reaction was unexpected. Standing ovations are common in theater, but in the middle of a show?

“I would say it very rarely happens. I think you have to drive on a lot of cylinders to get a mid-show standing ovation.”

Six weeks into the run of the musical, the response to “You Oughta Know” — and to Patten, specifically — hasn’t let up. Right after the big number, the house rises, and Patten waits with the ensemble of dancers frozen behind her until the audience calms down. The people who work in the ART’s offices down the hall say that sometimes, when they feel the rumbling under their feet during the climax of the song, they run to the back of the house to catch the reaction. It doesn’t get old.

For Patten — whose credits include “Fun Home” on Broadway and last year’s off-Broadway run of “The Wolves” — it’s a new acting challenge, because it’s a musical, not a rock concert, so she can’t bow with gratitude, no matter how loud it gets.

“My job is to stay in the story. It becomes a little bit of suspended time for me. You just sort of pick a spot on the wall, and it’s a great chance to catch my breath, too. . . . As an actor, I’ve never experienced [this] before.”

Audience members and Patten’s colleagues say the standing ovations aren’t just about the popularity of “You Oughta Know,” one of the most iconic tracks on Alanis Morrisette’s 1995 album “Jagged Little Pill,” which inspired the ART’s new musical. They say it’s about Patten’s full performance and treatment of her character.

The production — which features a book by Oscar-winner Diablo Cody, songs by Morrisette and Glen Ballard, arrangements by Tom Kitt, and choreography by Sidi Larbi Cherkaoui — is about a suburban Connecticut family navigating (and avoiding) conversations about addiction, sexual assault, race, and more. Patten’s Jo, who’s romantically involved with the daughter in the family, tackles questions of gender identity, fidelity, family, and friendship.

Patten, who’s from Chicago, worked with Paulus and Cody to develop Jo as a three-dimensional character exploring their gender. She said the big audience reactions might be led by people who are grateful for the story and the portrayal.

“There are a lot of people who come to the show who feel like they’re seen — and they haven’t been seen before,” said Patten, who spent last weekend marching in Boston’s Pride Parade and posing for photos with fans, who included Senator Elizabeth Warren.

The wild reaction to Patten is also about how she lets go. Jo spends much of the first act deflecting with humor, laughing off the daily heartache. Like the other characters, Jo avoids conflict by repressing everything.

“First of all, if I got to decide what I was, I’d be a koala,” Jo says, recounting a painful family conversation about gender identity.

Then, in the second act, after Jo is betrayed, it’s time for the song. Patten begins “You Oughta Know” almost motionless. She’s contained and furious as she sings those famous first lyrics: “I want you to know . . . ”

“She’s not even moving her head,” Paulus said, of Patten’s delivery of Cherkaoui’s choreography. “It’s genius. She’s not even looking at Frankie, the character she’s singing to. It’s so radical. It’s so strong.”

It builds, the movements still small, but then, as Patten reaches the climax of the number, surrounded by the company of dancers, she unleashes the fury. Paulus said she had to rethink cues with her stage manager after it became clear that the ovations would be big, and would continue. As a director, she wanted to respect the house.

“It’s a moment for the audience to say, ‘I hear you. I see you. I feel this, too,’ ” she said.

Now, because of so many reviews and social media posts about the production, some audience members know what’s coming and are ready for it. At a recent show, during the last moments of “You Oughta Know,” some were already looking around, preparing for the house to rise.

But Patten doesn’t take the response for granted. She knows that for every performance, she and the cast have to earn it.

“It’s never something that you would accept,” she said. “It’s not something you ever get used to. It’s wild.”