It was unlikely pas dequatre. In one corner, ballet superstar Rudolf Nureyev traded buck-and-wing tap steps with legendary black hoofer Howard "Sandman" Sims.

Nearby, musical comedy queen Julie Andrews and dancer Ann Reinking commiserated about the heat -- Andrews sipping tea from a Coors beer mug and Reinking, wearing the familiar bowler hat and close-fitting gray dance pants, stretching her legs on an improvised barre.

And sitting patiently offstage at Columbia's Merriweather Post Pavilion were dozens of dancers waiting to rehearse everthing from Martha Graham's "Seraphic Dialogues" to Bob Fosse's "Chicago" to clogging.

Some cast members dubbed yesterday's rehearsal "Mary Poppins Meets the Royal Ballet, the Happy Hoofer and All That Jazz." but CBS preferred "Julie Andrews Invitation to the Dance With rudolf Nureyev" -- part of their Festival of the Lively Arts for Young People.

The production, taped last night for broadcast in November, marks the latest tryst in television's love affair with dance superstars. It is, some say, CBS's one-upping of this year's ABC presentation of "Baryshnikov on Broadway" and NBC's "Evening With Jerome Robbins."

"Dance is very hot on TV," said Bernard Rotham, co-producer with Jack Wohl. "We're presenting a smorgasbord of dance for children -- tap, ballet, modern, jazz. The best way do this is through the top profesionals in dance."

An unexpected byproduct of this talent pool was a sharing of tips and techniques -- particularly between classical dancer Nureyev and hoofer Sims.

"It started during a skit," Sims said. "I was showing Rudy a basic buck and wing, and he caught on just like that. He even did it on both feet.

"He got real interest, and said, 'I'd like to try some more of that so whenever we came together we'd trade off some steps.

"He'd make a great tap dancer. He's got perfect knowledge of rhythm. But I'd have to break him of the habit of walking with his feet pointed out."

How did Nureyev like his tap lessons? "Fantastic," he said, rising practically on pointe, then moving swiftly into a gracefully executed time step. "Everyone here is a fine dancer."

To Reinking, this praise from on high proved particularly gratifying. "Nureyev's been an idol to me," confessed the raspy-voiced star of "All That Jazz." "I just can't believe I'm dancing with a legend."

Andrews also inspired admiration. "I can only dance," Nureyev winked. "But Mary Poppins can fly."

Although Andrews called Nureyev "the greatest dancer of our time," she delcined to single out one of her co-stars as a particular inspiration. Instead, with characteristic sweetness, she praised "all the wonderful guests on the show.

"I had forgotten how exciting live theater and dance can be," said Andrews, who remained astonishingly crisp on stage throughout the day-long rehearsal. ("Mary Poppins isn't supposed to sweat," she confided during the taping.)

At first, last night's packed house was wildly enthusiastic. The invitation-only audiience include dozens of youth groups and some children of the American hostages in Iran.

But repeated production delays dimmed the initial excitement. To entertain bored youngsters during the lulls, Andrews answered some of their questions.

Her favorite costar? "Dick Van Dyke and James Garner." How does she juggle her career and private life? "My husband and I have a pact so that when he's working, I don't, and vice versa."

When did she start in show biz? "When I was 7," she told a 10-year-old. "You'd better hurry up."