It came as a surprise to Atlanta Ballet dancer Alessa Rogers when Twyla Tharp, one of the western world’s most prolific and celebrated living choreographers, announced at a morning rehearsal last August that Rogers would dance the lead role, Princess Irene, in a studio performance of Tharp’s “The Princess and the Goblin.”

That afternoon.

“That was terrifying,” Rogers said, laughing, in a recent interview. The petite, fourth-year company member had about two hours to work out partnering sequences for a role she’d never done before.

Through the 75-minute private showing, Rogers could hardly believe it as she whirled weightlessly like a dervish, and later was tossed back and forth between partners to rolling melodies of Franz Schubert’s “Wanderer Fantasy,” seeming to blossom with each successive lift.

Afterward, Rogers said she thought, “If I can do it with basically no preparation, then I can do it in February.”

“I think Twyla did that just to see how I would handle it,” she said.

Rogers is scheduled to dance Friday in the world premiere of Tharp’s “The Princess and the Goblin” at the Cobb Energy Centre. Performances run through Feb. 19. This is Tharp’s first collaboration with the Atlanta Ballet and represents a major milestone for the dance company as it seeks to shape a distinct repertory profile featuring some of the nation’s most influential choreographers.

With Tharp in the studio mounting a world premiere, it’s pushing the company through a growth spurt that’s not without a few real-life trials.

“It’s very surreal to be working with Twyla,” said Rogers. “She’s a legend I’ve heard of since I was a little girl — almost mythical. But then she comes into the studio with sneakers and jeans on. She’s down to earth. She’s singularly focused, dedicated and committed to creating dances.”

Rogers described the “quick, subtle weight shifts” that make Tharp’s style difficult to master. Recently, Tharp asked dancers to change the accent in every musical measure from the first beat to the second.

“That’s just been utterly bewildering,” Rogers said. “I think she does that to challenge us and make sure we’re not settled into a routine. She always wants to shake it up and make sure that it’s fresh and spontaneous and new.”

Change is a constant for Tharp, whose choreography moves seamlessly through dance styles and genres that were once worlds apart — from postmodern, pedestrian movement to grounded, earthy shapes of modern dance, to the long lines, precision and rigor of classical ballet — all with the rhythmic complexity of American vernacular dance forms.

Tharp emerged from a culture of radical artistic experimentation in the 1960s. Her 1973 “Deuce Coupe” for the Joffrey Ballet marked the start of a trend that has gradually spun ballet and modern dance lineages together.

Tharp has since choreographed for some of the world’s highest ranking ballet companies and has had film and Broadway successes. Her 2009 Alliance Theatre premiere “Come Fly with Me” (now titled “Come Fly Away”) had successful Broadway and Las Vegas runs and is touring nationally. In addition, her autobiography and books on creativity and collaboration have helped to push her into mainstream American culture.

Tharp’s reputation attracted John McFall and André Lewis, artistic directors of Atlanta Ballet and the Royal Winnipeg Ballet, respectively. They proposed a shorter work, but Tharp saw in their offer — and in the community support evident in Atlanta Ballet’s new facilities — the chance to realize an idea she’d had for 20 years.

“The community wanted to have something very special built that would have a real substance to it,” Tharp said in an interview at Atlanta Ballet. “They understood that that takes work, and it takes support; and they were prepared to do that.” Atlanta Ballet and the Royal Winnipeg Ballet have evenly split the production’s $1.45 million budget. The RWB will perform the ballet in the fall.

Tharp chose a children’s story — unusual for her — that features 13 students in the cast. The youthful cast shows the spectrum of generations in a ballet institution, Tharp said, and illustrates how dance tradition passes from one generation to the next.

Based on George MacDonald’s 19th-century children’s fantasy by the same title, “Princess” is a coming-of-age story about a princess who confronts her deepest fears on a quest to rescue her younger sisters, her friend Curdie and about a dozen lost children from the goblin kingdom. Aided by her great-great-grandmother, she rises to maturity through a series of trials and ultimately teaches her elders a more compassionate and responsible way to live.

Tharp saw “a goodness” and a simplicity in Schubert’s music that was “in the same vein and spirit” as MacDonald’s story. Though not quite contemporaries, both are simple storytellers with a very “beautiful spine to what they do,” said Tharp. “They both have these extreme mentalities that went to fantasy, which is a component of romantic imagination.”

Composer Richard Burke arranged and orchestrated the score, combining Schubert’s pieces with Burke’s original compositions. The Atlanta Ballet Orchestra will perform the score.

For dancers, the process has been unpredictable and challenging. Last summer, Tharp and seven dancers worked intensively for five weeks, six hours a day, to build the ballet from the ground up.

“One thing that Twyla demands when you enter that door is total, absolute concentration and devotion to what that process is in the studio,” dancer John Welker said. “Part of that means letting go of ego.”

Tharp’s process can involve performing a succession of 20 steps after seeing Tharp show them only once; it might mean learning movement phrases from videos, then doing them backward or turning them upside down. It might mean learning 14 variations of a phrase, then being asked to go back to the sixth variation learned two weeks ago.

There were music history lessons and trips to the library to research goblins in English literature; some were assigned fictional book reports on their goblin character’s family lineage and personality quirks.

Some days, they’d repeat dance phrases exhaustively, only to throw them out and begin the next day from scratch. Welker said Tharp never stops demanding more from her dancers. “[When] you’ve reached a certain point and a feeling that you stop to grow, she is really quick to be on you, that you’re not here to just make shapes, you’re here to become a better artist,” he said. “Each time, she expects to see something different, something new. So if you build your character day in and day out, each time you repeat it, whether 10 times, 20 times, there’s a certain level of integrity that she demands and expects.”

Whatever trials each dancer faces, Tharp is likely to bring more nuanced performances from the dancers, in a more intricately structured and densely textured work than most have ever done.

“Twyla is so unique in the way that she works and in her intensity,” Rogers said. “This has definitely been one of the biggest roles that I’ve done so far in my career. Just the fact that I’m doing Princess Irene in a Twyla Tharp world premiere — that’s a lot to absorb. Really, it’s been a whirlwind.”

Dance preview

“Twyla Tharp’s The Princess and the Goblin”

Atlanta Ballet

8 p.m. Feb. 10; 2 p.m. and 8 p.m. Feb. 11; 2 p.m. Feb. 12; 8 p.m. Feb. 17-18; 2 p.m. Feb. 19. $20-$120. Cobb Energy Performing Arts Centre, 2800 Cobb Galleria Parkway. 1-800-982-2787, www.atlantaballet.com.

Cynthia Bond Perry is dance critic at ArtsATL.com.