She stomped to accentuate rhythms. She sang out the notes. She counted, inserting the word “and” in all sorts of unfamiliar places to emphasize new accents. And though she is in need of a hip replacement, Patricia McBride moved like the wind.

“Ta, ta, ta, ta, ta,” she called out emphatically and repeatedly during a recent rehearsal for George Balanchine’s “Rubies,” with dancers from New York City Ballet. In 1967, when Balanchine choreographed this segment of “Jewels,” Ms. McBride was its female lead.

As she helped the dancers, it became instantly clear that the most paramount — and fragile — part of a Balanchine ballet is its musicality. Heading into City Ballet’s fall season, which continues through Oct. 14, Ms. McBride worked alongside Edward Villella, her long-ago “Rubies” partner, to put the choreography back on its beat.

“I just have to think of it differently, but I love it,” Sterling Hyltin, a principal dancer, said during a coaching session. She was struggling but avid: “I have to get all of this in my body. I need to practice it.”