Elphaba might have been reluctant to go to Shiz University, but Cynthia Erivo still wants to get a doctorate.

Specifically, the star who plays Elphaba in “Wicked” on screen is interested in how everyday experiences affect people’s voices, not just when they are speaking but when they are singing, too. Erivo was keen to study this after being accepted as a fellow into Harvard University’s Radcliffe Institute for Advanced Study in 2021, but she had to decline the fellowship because of a busy schedule that never slowed down.

Although filming for “Wicked” is over, she went on a huge media tour for Part 1, she’s in the thick of an awards season campaign, and she faces the prospect of another media blitz when Part 2 opens later this year. She’s also starring in, producing and adapting a film version of the Tony-winning drama “Prima Facie.”

But it was her work as a teacher at her alma mater, the Royal Academy of Dramatic Art in London, that was still on her mind. “Every time I can tell,” she said in a recent interview, “when someone has been told that they are too much, they should be quieter, or they shouldn’t talk so loud. It transfers over to how they use their voices when they sing.”

She explained that when students get to a belting note, they seem to back off. “The notes are there. The sound is there,” she finds, but then “they put it in a song. It disappears.”

Meeting up in November, a week after “Wicked” opened to a strong $114 million domestically, Erivo was surprisingly as eager to share her theories of vocal psychology as she seemed at ease with her sudden global superstardom.

Even without Elphaba’s green makeup, microbraids and black dress, Erivo was instantly recognized by the patrons at Sardi’s in Manhattan’s Theater District in New York City, where we spoke. Downstairs, her caricature hung on the restaurant’s celebrity wall, an honor she received after winning the 2016 Tony Award for her performance as Celie in the Broadway revival of “The Color Purple.” (She also has an Emmy and a Grammy for performances related to the role.)

What links “The Color Purple,” “Wicked” and other key career moments has been her ability to move seamlessly between the characters’ reserved personalities and their impassioned expressions of their inner lives. Sitting with Erivo allowed me to appreciate the qualities she shares with them: a keen intellect and inquisitiveness. These traits are most present in the screen performances for which she may be best known: bookish Elphaba, prodigious Aretha Franklin in the 2017 miniseries “Genius: Aretha” and prophetic Harriet Tubman in the 2019 biopic.

“I don’t pick the characters frivolously,” she said. Their intelligence, though manifested in different ways, allows her to get into their psyches “so that hopefully a watcher can leave, think that they’ve forgotten, but a day or so later, they are still thinking about that character and what the character has been through.”

Erivo explained that she didn’t want the characters to disappear but “to stay with you and maybe help you address some things, remember some things, change some things.” She conceded that she might be asking a lot of the characters, but to her, “that’s kind of the thrill of it, hoping that that might be a possibility.”

That also describes her effect on the “Wicked” creative team after her audition. The film’s director, Jon M. Chu wasn’t sure whether Erivo, who was 35 at the time, would be open to a character that young and innocent again, especially amid, as he put it, “the different vibe” of Oz.

“She completely transformed my opinion of what she’s capable of doing because she came in jeans and a T-shirt,” Chu recalled. “She looked like a little girl, and the way she sang ‘Wizard and I’ wasn’t like the untouchable Cynthia Erivo.”

“She just completely made me believe in Elphaba’s yearning for a better place and optimism at the movie’s beginning,” he continued, “We were waiting for someone to come into the room and take the role from us instead of us coming up with excuses of why we should cast someone. We just wanted to see a person be it, and that’s what she did.”

Erivo has spent her career pushing past others’ expectations: first by landing the role of Celie, in the 2013 revival of “The Color Purple” in London, then bringing the house down for almost two years after the show moved to New York in 2015. Four years later came backlash when the British-born and raised Erivo, who is of Nigerian descent, was cast to play Tubman, the celebrated Black abolitionist who escaped from slavery in the American South. But Erivo received Oscar nominations for both best actress and best song.

Although she wore extensive green makeup and prosthetic ears in “Wicked,” Erivo’s shapeshifting rarely involves a radical physical transformation. Standing 5-foot-1, she tends to come across as larger than life because of the icons she plays, her meticulous research process and her intense prep long before filming.

Kasi Lemmons, the director of “Harriet,” said she was blown away by Erivo’s ability to infuse minor details into scenes that were complex and harrowing to shoot. “The first thing we did was have Harriet lead the freedom- seekers across a big field,” Lemmons said. “And when Cynthia came on, she was Harriet, but then she ran. It wasn’t the athletic run that I had seen her do in a movie like ‘Widows.’ There was something feminine and ordinary in her run, even in how she held her dress. It was a beautiful swiftness. She brought a softness to Harriet that I thought was essential, but I didn’t know how essential it was until it unfolded in front of me.”

Erivo has a similarly mesmerizing moment in “Wicked” during “The Wizard and I,” a showstopper revealing Elphaba’s ambitions, loneliness and self- consciousness. But, for a brief second, it does even more: When Elphaba looks in the mirror and sees her skin change from green to brown and back to green again, the film recognizes the power of casting Erivo as the rare Black actor in this beloved role.

Visiting the “Wicked” set last year, Leslie Odom Jr., who starred with Erivo in “Harriet” and the John Ridley romance “Needle in a Timestack” (2021), saw them shoot that scene.

“It was just the joy of watching someone who has obtained mastery over a handful of the disciplines. When it’s done at that skill level, I find it very moving,” he told me. “But I also saw a tenderness and an acceptance of herself, which means the work is not tortured. I felt as though I was witnessing someone allow themselves to be enough.”

And although Erivo’s “Defying Gravity” finale in “Wicked” is an unforgettable combination of virtuosity, vulnerability and charisma, Chu pointed out that “she’s never stopped doing the work to master a scene.”

He added, “That takes resilience, dedication and a promise to that character to see her through. By watching her, we all had to commit to that level, and it raised the bar for everybody.”