Audiences--at least the men in the audiences--undoubtedly have fantasies about Cleo Laine. They may be interested to know that the British singer also has fantasies about them.

"I like to imagine when I'm singing that it's not thousands of people but one person," she said in her suite at the Guest Quarters, "and a love affair can be created that way. I ignore my husband in the background; this is a love affair going on."

Tonight Cleo Laine will continue her love affair with thousands of people in the Kennedy Center Concert Hall. Her husband--composer, arranger, saxophonist and band leader John Dankworth--may be in the background, but he will be conducting the affair, which he has already orchestrated. The current romance began some time ago in Detroit and will continue in San Francisco and on through a tour of Australia.

"Sometimes there is an electrical current between the audience and me," Laine said. "It happens a lot more in America than it does in Britain; of course, they're very reserved there, and they won't let their electric currents come to you, even though they've got them inside. Americans, Australians, too; they're more extrovert and will show their emotions more easily. It does happen quite a lot in America, and you feel that they are sitting there urging you to greater heights."

This kind of electricity has been flowing in Cleo Laine's life since she was born Clementina Dinah Campbell in England in 1927. Her father was a singer from Jamaica, her mother an Englishwoman; both were musically talented.

"I guess I inherited his voice," Laine said. "The household was musical, we always entertained ourselves, and he would sing at the drop of a hat. He was a good singer, although he never achieved what he wanted to do, which was to sing professionally.

"He was a busker, singing on street corners in the Depression. It was a matter of need, dire need, in those days. Being black, it was difficult for him to get work, so he busked. I wasn't really aware of this until much later, when I realized that he used to bring a lot of pennies home and count them. Then I knew. He must have made a lot of money, because we were generally clean--at least reasonably clean."

With this background, there was never any question of what Cleo Laine wanted to do with her life. "I never dreamed of doing anything else--not singing, so much, but being on the stage. Even at school when people asked, 'What are you going to be?' most of them said 'a hairdresser' or 'a secretary,' 'a nurse' or 'a beautician,' but I would always say, 'I'm going on the stage.'

"I was laughed at, because this was a pie-in-the-sky dream. My mother did apprentice me to a hairdresser, but during all the other jobs I had prior to my first break, I would audition . . . ad nauseam."

Her show business career began when she auditioned for Dankworth, whom she married years later. They have not always worked together (they married, actually, when she left his band to take her first role in a play), but her singing with Dankworth is the recurring motif of her career. They work together beautifully; they have the instinctive, almost telepathic rapport of true jazz musicians, and his arrangements support her voice, highlighting it like a jewel in a fine setting. The partnership has also produced two children who are beginning careers in music and theater: a 20-year-old daughter, Jackie, and Alec, 23, who sometimes plays bass in the Dankworth band.

"John said that when he heard me, I didn't sound like anyone else who was singing at the time," Laine recalls. "I guess the reason I didn't get the other jobs is that they were looking for a singer who did sound like somebody else."

She still doesn't sound like anyone else--or, rather, she sounds like many singers--any kind of singer she chooses to be. Her latest album, "Smilin' Through," focuses on such standard pops as "I Can't Give You Anything But Love." But her repertoire includes a lot of scat singing and other forms of jazz, Arnold Scho nberg's formidable "Pierrot Lunaire," one of the cornerstones of 20th-century vocal music, and Sir William Walton's "Fac,ade," one of the trickiest musical settings of English words in our time--not to mention a whole program of music with words by William Shakespeare. She delivers this material in a voice that spans some 4 1/2 octaves.

This kind of variety did not enter her career until she had sung for several years with Dankworth. The broader career "got started by accident, really by need," she said.

"My ambition was not really to be a band singer all my life, although I'm really grateful for it and it was probably the best school that any singer could have at the time. You sang a multitude of different material--both great and yuck. You got used to touring and finding out that a lot of it was rubbish and nastiness. I felt that there were better things."

At that time, a London company was having trouble casting the lead role in a play about the West Indies; someone suggested her name and she was an instant success.

"I thought I had it made," she said. "That was it--I was going to be the next Sarah Bernhardt, of course. And I waited for two years before I got another chance."

The next role was "in a tacky touring play about South Africa that really wasn't very good," but her potential finally began to be recognized; she was given roles in classics by Shakespeare and Ibsen, and finally the music and acting came together when she substituted for Lotte Lenya, with only 10 days to prepare, in the Edinburgh Festival production of Kurt Weill's "The Seven Deadly Sins." Eventually the time came when she was singing at the Sadler's Wells opera house and simultaneously had a record in the top 10 in Britain. "It seemed as if that was how my career was going," she said, "and I thought, if I could do that, why should I stop?"

She still sees no reason to stop and has no problem choosing among popular music, classical music and straight theater: "Whatever I'm doing at the time is my favorite thing. A lot of people would say I'm too eclectic, diversifying too much, but I think that because of that I've worked longer and had a much more interesting life."