Cheryl Barnes is sitting in director Millos Forman's aerie overlooking Central Park. Like Dorothy in the Wizard of Oz, she knows that this is not Kansas.

"This promotional tour is good for the movie and great for me," she said flatly.

After almost a decade as a nameless voice with a lot of promise in New York theater productions, Barnes sang one song in her first movie, Forman's film version of "hair,c which stunned audiences and critics alike and drew her comparisons to Aretha Franklin. Now, she has an agent for the first time, the same man who handles Forman.

There is a shopping spree in the next couple of days, compliments of the United Artists publicity juggernauts, at stores along 5th Avenue which inflation czar Alfred Kahn would label obscene.

She'll be in California next week taping an appearance on the Dinah Shore Show, and then it's off to Paris, the Cannes Film Festival, Prague and other European watering holes for the rest of the promotional tour.

It would appear that Cheryl Barnes has arrived. Yet at 28, she has a reserve about her that speaks pointedly to the new glamor in her life. It says, don't take this too seriously, because you could be working as a chamber maid again before you know it.

She is candid enough to admit that she wants success in the worst way, but wise enough to know that despite the tinsel that drapes her life now, her future success is not a foregone conclusion by any means.

She has yet to find a manager, and despite the raves that have piled up following her performance in "Hair," she has had no firm offers to do anything else so far. "There are not enough parts out there for black singing actresses," conceded Robert Lantz, her agent.

The modest amount of money she received for the film is long gone; in fact, she was waitressing at Happy Donuts in San Francisco to pay her bills when United Artists plucked her up for the tinsel tour.

The money did allow her to live for almost a year in the sovereign community of Barstow, Calif., dead in the center of the Mojave Desert, where she sequestered herself with a toy poodle, a cat and a piano. After filming there ended in April of 1978, she simply stayed on.

"I like to follow the line of least resistance," she explained.

Up to a point. But it is doubtful that she would have put up with the fears and frustrations of nine years on the edge of the New York theater world if she really were a creature of convenience. The mania that weaves klieg lights with unemployment lines is romantic, perhaps, but hardly comfortable.

Barnes grew up the oldest of five children in a middle class family in the middle class town of Westfield, N.J., "where everyone is supposed to go to college." After one semester at a nearby state campus, she left for the theater and landed her first role in an off-broadway play called "The Last Sweet Days of Isaac" in 1970.

A shot at a solo career is the dream of anyone who has been swallowed up in choruses of productions like "Godspell," Leonard Bernstein's Mass and a concert version of "Jesus Christ, Superstar," and sang back-ups to Leonard Cohen. And so when Harvey Feuer, casting director for "Hair," sent her a telegram in the spring of 1977, it was not hard for Barnes to stop playing chamber maid on Martha's Vineyard and promptly return to New York.

She survived five auditions to win the role of Hud's fiance, a part that was created in the movie. It is not a large role, but she made the most of it, and sat in front of a mirror for weeks perfecting the lip synch she would use in front of Forman's cameras. Finally, on a freezing December day in Greenwich Village's Washington Square Park, she stood in the snow and sang "Easy to Be Hard," a song that she turned into a showcase for her vocal and emotional ranges.

"My teeth were chattering, and I was afraid that it would show," she remembers. "God, it was cold that day."

Unlike most of the other numbers in the movie, Barnes had the song all to herself. It lends itself to saccharine, and as such, is fraught with peril for a performer. But she sang it as straight as the part she played, and the result was a refreshing foil to the constant flakiness of the rest of the film.

But the glowing comparisons to Aretha Franklin and even Mahalia Jackson, are mixed blessings as far as she is concerned.

"I'm black, and I sing out, so everyone says I sound like them," she said. "I don't think I do. Besides, I don't want to sound like someone. I want to sound like Cheryl Barnes."

Still, she's not complaining; the song put her on the map. She took the job without hesitation or an agent to advise her and worried about the details later, something she hopes never to have to do again.

"They handed me a contract, and I signed it," she said. "That is definitely not the way to do it, but I wanted this opportunity to act very much.

"The money was not important, but there were other things" she continued. "There is more respect for actors who have agents. Your job is easier for you. Then there were perks like dressing rooms, thing like that. I made some mistakes."

But her experience in "Hair" was an important introduction into a new medium as well as a giant step up, and she liked what she saw.

"I feel that is is easier for me to be natural in a movie," she said. "I like being able to express myself in a low-key way.

"I'm still exhausted from the theater," she continued. "You have to project yourself eight times a week. I don't drink or smoke when I do theater. I need to sleep late so I don't enjoy the day. There's always an obligation to the audience."

If the tinsel stays and she has a choice, Cheryl Barnes will try straight film acting and album work next. She wants to be seen and heard by herself. But at 28, she is neither a star-struck kid nor a jaundiced veteran, and this is something of a problem for her.

"I'm not sure what it means to other people that I'm 28," she said. "I want to be given the opportunity to play younger parts, but I can't wait for my wrinkles either."

Like many other would-be stars, Barnes has no love life; her single-minded pursuit of stardom all but precludes serious involvement with a man for now.

"If I were to get involved with someone, he would have to have a real understanding of the business if he weren't in it himself."

But then she has always been a loner; she has gained sustenance from herself and currently from her beloved poodle, Mauffy, which is now with her sister in San Francisco. When she needs to spill her guts to another human, she's not very particular.

"I find that I can do that with whoever I'm with," she said. "I will say, 'I've just got to tell you. . . .' It's uncanny how they get to the point of things."

It is tempting to treat Cheryl Barnes as a cliche-the struggling member of the chorus lines who grabbed an opportunity and is riding it hard. But then she ruins the image by hibernating in the desert for almost a year instead of hustling with a vengeance for an agent or another script.

She wants success, but in her own words, "there is no offer which I couldn't refuse in the theater right now." CAPTION: Picture, Cheryl Barnes in New York, mapping the road to success. By Donal F. Holway for The Washington Post