THE LIMBS of Judith Jamison sprawled across two chairs in her Kennedy Center dressing room. In a moment the sprawl became a stretch, and then a pose. The limbs then redeployed into new angular designs, elongating and unfurling. Out of this lolling recumbency cocked an elbow from behind her head, perfectly balancing a warm-up-suited leg stuck out like a cantilever to support a gigantic ball-of-fluff slipper. The movement was fluid and subtle, with the tempo of time-delay photography.

Judith Jamison is a dancer, and for her there is movement even in repose..

In order to assure that movement continues, she resigned last June from the Alvin Ailey Dance Company, where during 15 years she had become a star. The tall, lithe, extraordinarily dramatic figure of "Revelations," "Cry," and 50 other works by Ailey and others, she played to sell-out crowds. And walked away.

"I just slipped right out," Jamison said with a smile. "No goodbyes. No au revoirs. Why? Because I had to do a Broadway show."

The show is "Sophisticated Ladies," a musical celebration of Duke Ellington featuring 49 of his songs and a big band fronted by Jamison, Gregory Hines, Phyllis Hyman and P.J. Benjamin, among others. It opens Tuesday at the Kennedy Center. Jamison will sing as well as dance, and act a bit, too.

The audiences will see, as she puts it, "that I can talk, that I'm not mute." And Jamison, from the other side of the footlights, will have a glimpse of alternative futures. She is 37. The alternative futures will be hers. "I want to do anything I can from here on, and I'm open to suggestions," she says.

"Sophisticated Ladies" calls for Jamison to sing, in addition to the title tune, such Ellington classics as "Black Beauty," "Solitude," "Black and Tan Fantasy," "I'm Beginning to See the Light." But it's not as if she is without experience.

"Well, I used to sing on the bus with the Ailey troupe," she explained tentatively. "I sang in the shower. Really, I've been studying voice for about a year and a half now, and I find I have a very loud instrument. You have to study technique for the same reason dancers do. Maybe you can do one pirouette, but it takes technique to do five and keep from falling on the floor.

"My professional singing debut was last week in Philadelphia," she added. "It was on Maury Povich's television show there -- I'd met him when he had the Panorama Show on Channel 5 here. They stuck a mike in my hand, and told me to sing. So I did."

She's also been preparing for whatever needs the theatrical world may have of her. But more of less in secret.

"I've done two off-off-off Broadway plays already, just for the practice. One was an experimental 'Romeo and Juliet'. They were hidden away in lofts in New York, and nobody noticed, which was what I'd wanted. After all, I'd worked up my reputation as a concert dancer."

Did Jamison get to play Juliet?

"Oh no, no," she said. "I played her friend. But I did find it an interesting experience in trying to become another person. In dance, when they told me to portray someone else, it always turned out to be me."

Jamison, however, still thinks of herself as a dancer, and has no plans to give that up. "When I look at people who aren't in the dance world, they look different to me. I can't help it, they do. I don't ever want to lose that. I mean if you don't work out and keep moving, you get out of shape. You lose something."

She says there was no animosity in her departure from the Ailey company.

"You're supposed to stay there a couple of years and move on. I stayed 15," she said, "and they spoiled me. When Alvin came up with 'Wading in the Water' part for me in 'Revelations,' I actually felt demoted, because I'd done 'Fix Me Jesus' already for two years."

"Wading in the Water," however, turned out to be an Ailey masterpiece, which the public seemed to demand on every program. Its highlight was Jamison, swathed in white, an unforgettable picture of movement under a towering parasol. It became the company's signature piece and Jamison's biggest hit.

A native of Philadelphia, Jamison comes from a middle-class environment which exposed her to the arts. Her father was a part-time opera singer and concert pianist, and her mother a singer. Young Judith studied violin and piano, but it wasn't until she'd spent three semesters at Fisk University that she devoted hereself to dance. Actually, it was Agnes DeMille who discovered her at a master class and got her a role with American Ballet Theatre in New York.

"Ballet was just really something for me," she said. "I haven't been in a tutu since I was 17, and I haven't danced on point since 1966, but I loved it. I was a real turner."

A turner?

"Sure. You know, someone who can do pirouettes. It depends on a lot of things -- the floor, even the humidity -- but a good turner can rotate 10 or 12 times in one preparation. Somebody like Misha [Mikhail Baryshnikov] can do grand jetes, and just hand up there, we call him a jumper."

Jamison doesn't mind talking about the past -- "hey, that's what I've been doing.I don't want to forget it" -- but she insists that her departure from the Ailey company for an uncertain future was less a shock than it might seem.

"I actually left the womb back in 1968," she said. "That was when I first started guest-artisting, or whatever you call it. I found out somebody would pay me $200 for five minutes of dancing on another program. That's how we dancers make money, you know. Otherwise, we're broke."

The "next step" is something all successful dancers eventually have to consider, but for Jamison the natural progression was not to choreography, she said. And it wasn't to teaching, either. "But I could do coaching, I think. After all, I taught 'Cry' to five other girls, and 'Lark Ascending' to four." She also has some experience in arts policy and decision-making, having been appointed to the National Council on the Arts by President Nixon in 1972.

But Jamison seems quite unconcerned about precisely what her own "next step" will be.

"Sure this is an important transition period for me. It's new territory. But I'm not too scared. It's just another point to jump off of, and I like jumping off points. I'm just being receptive to anything."

How about a made-for-TV movie?

"Sure," Jamison said. "Why not?"

Her dressing room at the Kennedy Center is the same one she occupied 10 years before, when the center opened. She then performed in the Ailey dances that accompanied Leonard Bernstein's "Mass."

Now the dressing room is a temporary respite from the rehearsals for New York-bound musical. The company had just arrived from 16 straight performances plus rehearsals in Philadelphia, and the schedule had her returning to the rehearsal room at 7 p.m. and working until midnight. "That doesn't bother me," she said. "That's where discipline comes in."

Judith Jamison seems quite unconcerned that fate will deal her anythng but fair cards from here on. If she is most disinclined to discuss her personal life ("that's my business"), her professional future is an open book: available.

"What do I want to get out of all this?" she asked, repeating a question. "I guess . . . to be bowled over by love, that's all. Don't think I haven't thought about the future just because I don't talk about it. I don't like to talk about things before they happen. It's like whistling in the dressing room. It's just bad luck."