Fifty years ago, when director-choreographer giants still walked the earth, two of the biggest — Bob Fosse and Michael Bennett — created highly influential shows that have attained legendary status and lasted: “Chicago” and “A Chorus Line.”

These were musicals with dancing at the center. The showbiz-cynical attitude of “Chicago,” a tale of 1920s murderers who go into vaudeville, was inseparable from its choreographic style. “A Chorus Line” was about Broadway dancers, built from their real-life stories and framed as an audition.

To celebrate the golden anniversaries of these shows, The New York Times invited Robyn Hurder, who has performed in productions of both over the past two decades (and received a Tony nomination for her performance in “Moulin Rouge”), to demonstrate and discuss what makes the choreography so special. To coach her, direct-lineage experts were on hand.

For “A Chorus Line,” Hurder could turn to Baayork Lee, an original cast member who has been staging and directing the show ever since. (She’s directing an anniversary benefit performance on July 27.) For “Chicago,” Verdon Fosse Legacy — an organization dedicated to preserving and reconstructing the choreography of Fosse and his chief collaborator, Gwen Verdon — sent Dana Moore, who worked with Fosse in his 1978 “Dancin’” and his 1986 revival of “Sweet Charity.” She also danced in the 1996 “Chicago” revival and in revivals of “A Chorus Line,” too.

“A Chorus Line,” which Bennett choreographed with Bob Avian, is “all about angles and patterns,” Lee said. You can see them in Hurder’s one-woman rendition of the ensemble finale, “One.” Each moment is a picture, a geometric arrangement of head, elbows and knees, executed with the crisp precision of the Rockettes. Lee reminded her about the exact positioning of her fingers on her imaginary top hat, but Hurder didn’t require any coaching to give the moves the snap that makes them sparkle.

“Music and the Mirror” — the solo in which Cassie, the veteran dancer humbling herself for a job in the chorus, expresses her love for dance — is much more of a workout. “Everything is so fast and you hit everything so hard that it’s like you’re a little tornado,” Hurder said.

“You have to rely on your technique to get through, but if people don’t believe that you’re lost in the music, it isn’t right,” she said. And if the performer does get lost? “It’s like being close to God.”

Switching to the “Chicago” choreography, Hurder had to pull way back. “Don’t muscle it,” Moore told her. Fosse’s choreography stresses cool restraint, subtlety and minute detail. Moore adjusted Hurder’s shoulders by a fraction of an inch to achieve the perfect balance of seduction and aloofness. Body parts are isolated, as you can see in the snapping, twirling, ignition-starting fingers of the opening number, “And All That Jazz.”

To calibrate specifics, Hurder remembered visualizations passed down from Fosse (who died in 1987) and Verdon. One position should “hurt like you’re squeezing an orange between your shoulder blades,” she said. A bent wrist isn’t just limp; the dancer must imagine water dripping off fingertips.

And just because Fosse dancers don’t move much doesn’t mean they aren’t radiating energy, what Verdon once described as putting the car in neutral and revving it.

“There’s so many feelings in one little finger turn,” Hurder said. “And what’s so fun is to enjoy the power of that, holding eye contact with an audience member and making them uncomfortable.”

“Hot Honey Rag” is a string of slinky, snaking jazz and burlesque steps — turned-in knees, rolling hips, shimmying shoulders. Many of these moves, still immediately identifiable as belonging to Fosse style, were borrowed from vaudeville entertainers like Joe Frisco and Black dancers like Snakehips Tucker on whom those performers modeled themselves. But it’s as if these steps have been cleaned and touched up by a master art restorer and set in a new frame.

Fosse’s choreography, Moore said, adheres to an idea expressed by the acting teacher Sandy Meisner: “living truthfully under imaginary circumstances.” If the dancer is “muscling it,” then “you’re not living truthfully,” she said. “We rehearse and rehearse to get the specifics so into our bodies that we can let go.”

Asked to compare the Fosse and the Bennett choreography, Hurder reached for opposites: inward vs. outward, quiet vs. loud. Both are equally challenging, she said. The seemingly simpler Fosse steps made Hurder sweat and ache as much as the Bennett choreography did.

“When you do it right — ow!” Hurder told Moore as they rehearsed. “But after the ‘ow,’” Moore replied, trailing off in a smile. (“After the ‘ow,’” Moore explained later, “you come to this other place of ‘I didn’t know I could do that and feel that way.’”)

Despite these differences, “Chicago” and “A Chorus Line” are of the same era, created for dancers with a similar background and training. Lee recalled how some of the participants in the original Public Theater workshops for “A Chorus Line” jumped ship to join “Chicago,” which was already heading for Broadway. It’s that shared background, Moore said, that anyone trying to teach the choreography can’t assume current-day students will have.

One major difference in demonstrating the two styles is that with Fosse, there are several official versions to choose among. He made adjustments for particular performers, like Liza Minnelli, and the directors of various productions have made small changes. Moore’s assistant, Alyssa Epstein, said that Verdon Fosse Legacy is ecumenical about the variants: “We like to say, ‘All versions are valid.’”

Another big difference is that Fosse had a signature style, whereas every Bennett show was different. “Promises, Promises” didn’t resemble “A Chorus Line” which didn’t resemble “Dreamgirls.”

That’s one reason, along with Fosse’s film work and the still-running “Chicago” revival, that Fosse is more present than Bennett in today’s culture. Lee pointed out that revivals of Bennett shows often choose not to use his choreography. Except, that is, for “A Chorus Line.”

“I was there when it was being created,” Lee said, “and I have kept it true to form.”

Piano accompaniment by Caleb Hoyer. Audio by Kate LoPresti. Produced by Laura O’Neill and Josephine Sedgwick.