Alexei Ratmansky walked into the studio and got out his phone. It was the first rehearsal of his latest work for New York City Ballet, and the dancers were waiting eagerly to find out what he had in mind. He pressed play, and a woman’s voice and a piano, mimicking her vocal intonations, filled the room. “This is the music,” he told the assembled dancers.

“We were like, what?!,” the dancer Sara Mearns said. “How am I going to dance to this?”

“He also said, ‘There is no musicality, just your own,’” Ms. Mearns continued after a recent rehearsal. “In working with him on a whole bunch of ballets, all super connected to the music, it was the first time I had ever heard him say that. I thought, who is this person?”

“Voices,” set to Peter Ablinger’s “Voices and Piano,” which will premiere at City Ballet’s New Combinations evening on Thursday, is a new frontier, musically, for Mr. Ratmansky — known for witty, poetic physical responses to more conventional scores and sensitive reconstructions of 19th-century classics.