Two tacos and a chocolate soda remain untouched on the table. Natalie Cole, the singing scion who rekindled the Cole name a few years ago with fast, blessed success, slips a skinny leg, packed in blue duck pants and blue running shoes, over the chair. She laughs, suggesting the irony of her smash hit, " 'Sophisticated Lady,' huh?"

The titter, the casualness of her pose, and the steady, almost hard glance, seem to indicate Natalie Cole is okay. She's working very hard to hold onto the initial, meteoric acclaim, a process that involves the six weeks of one-nighters that started to wind down with last night's date at the Capital Centre. During this grueling period, Cole split with Marvin Yancey, her husband, co-producer and writer.

"I don't want to talk about why-the personal reasons for the separation. I'm being very optimistic; it's not affecting me from a career point of view," says Cole. A stern tone has replaced the lightheartedness in her voice. "I am a eechristian. I believe if Marvin and I were to be together, we would. And whether we keep working together-that's up to us, and we are working on it."

Her tranquility under stress, the public ease the musters, evolves from the knockless road of her own life. Hers is not the typical story of the black entertainer who learned the blues from living it. She grew up in the comfort of Los Angeles. Hers is not the story of pounding on producers' doors with a demo. Her father's label, Capitol, was only too glad for another Cole mine. The things she had to learn are more personal, more in tune with the '70s. "You have to amp yourself on the road, learn how to be the best each night. And I think the whole rush of getting ready helps me," she says.

Her answers about Yancey, a minister who reportedly spurned another woman for Cole, are delivered quickly and evenly, as are those about her entertainment future, the past encumbrances of being compared with her father, the pain of an unwanted feud with Aretha Franklin over black female singing superiority. There's a sweet, womanly toughness in this 29-year-old headliner. She talks about discovering her legs. "When I played at the Metropolitan, my gown had slits up to here for days. People discovered I had legs; I began to like it. Then my stage clothes-well, they have not gotten extravagant, but when I went back to the designer I said, 'give me some more legs'," she says impishly.

Quickly, with an almost embarrassed rush, she sets the record straight: "My main concern is the music." Ever since she began recording in 1975, Cole has been defining her style, and fighting those who want her to imitate her father, Nat "King" Cole, the foggy-toned crooner and racial pioneer. The burden of legacy also has happened to Nacy Sinatra, Liza Minnelli.

"I could understand it if I were a boy," says Cole, harried by this inevitable question. "But with me we are so totally different. He was strong, paced. I'm looser, funkier." in the beginning, people would come up to her and announce, "You'll never be as good as your father." Says Cole, "I was hurt because I wasn't trying to be, but that made me think, am I trying to do that?"

Some justification came, just one year after her start, when she won two Grammys. That was followed the next year with the award for the best rhythm-and-blues female performance. Enter the Aretha Franklin comparisons.

"Comparisons are okay, but people made it into a feud. We are all different-Aretha, Chaka (Khan), Donna (Summer), Thelma (Houston), me. It doesn't matter if you are black or white, Laura Nyro isn't Judy Collins," says Cole, who before the Grammys had won her only contest with a college rendition of Franklin's Rock Steady." "And I reacted like an individual, I got mad. I guess I was a little too sensitive."

Yet Cole knew she had to prove that burst of publicity, expectations and awards were deserved. "When it all sunk in I knew I couldn't go out and sing 'mary Had A Little Lamb.' I had to build a consistency," says Cole. "I wanted each album to be different, I wanted each to have a message. Marvin was a great help. He knew what I was thinking." Her voice doesn't have the power and versatility of some of the thoroughbreds in the field. She knows that. "I'm in no way in technical control like Shirley Bassey or Barbra Streisand. But with my kind of material right now, I have to be loose," says Cole.

The perfect exposure of her family name and the excellent first notices brought their own perks. She appeared on a frank Sinatra special. "I was thrilled to pieces, but I worked. They sent me a tape of the song we did together, 'I Get a Kick Out of You.' I listened to it four times, memorized all his pauses and licks. And when we were finished, he looked at me and shook his head. I was ready for him because I knew he's impatient. And all I could think was 'Daddy would have been extra proud'," says Cole

In her show, which she takes on a month-long tour of Europe in two weeks, Cole gives credit to her writers and producers, Yancey and Chuck Jackson, a half brother of Jesse Jackson. She didn't stop when her personal life was tormented. "Not at all. As a matter of fact, I probably overdid my performance so no one would know the problems, and my praising. I didn't stop giving credit," says Cole.

An errant ray of sunlight has picked up the green in her luminous, smoke-gray eyes. She looks glowing as she gives Yancey his due. "Marvin is a real musician, like my father. He used to play on the window sills because he didn't have a piano," says Cole, spiritedly. "He's a genius. I gave something to him, he to me. It would be a shame to break up a successful musical partnership, but it's just something we are still working on." CAPTION: Picture, 1, Natalie Cole, by Gerald Martineau-The Washington Post; Picture 2, Natalie Cole, by Gerald Martineau