"My Ideal," from the Paramount picture "Playboy of Paris." Lyrics by Leo Robin, music by Richard A. Whiting and Newell Chase. Copyright (c) 1930 by Famous Music Corporation. Copyright (c) Renewed 1957 by Famous Music Corporation.

Backstage at Wolf Trap, in dressing room G. Margaret Whiting studies herself in the mirror. She checks out the eyes, encased in thick false lashes, the lips outlined in bright red, the body in a clingy blue pants-dress slashed with a rhinestone-encrusted white sleeve.

"I started out wearing pants because I was the only one (in the show) who wore pants," she says. "Ten minutes, please," says a voice over the intercom.

Whiting takes out a small travel toothbrush, puts it together and goes into an adjoining bathroom to brush her teeth. She comes back and pats more powder on her face. She is asked what sort of vocal exercises she does. "It's so eeeasyyy," she sings. "Hello, hello, hello."

A few sloshes of Christian Dior perfume and she's ready. The audience, nearly a full house and mostly over 40, is ready.

Whiting is the opening act of "4 Girls 4," in which she and three other veteran performers - Rosemary Clooney, Helen O'Connell, and Rose Marie-woo the audience with a combination of nostalgia, music and self-deprecating humor.

They're all in their 50s (Whiting is 54, Clooney 51, the other two in the same vicinity), and unabashedly took it. O'Connell's cheekbones have served her well, and she retains a kind of fragile prettiness. Rose Marie still wears the bow in that stiff blonde hairdo so familiar to viewers of "The Dick Van Dyke Show" and her 12 years on "Hollywood Squares." Clooney is hefty and Whiting's no sylph.

Among them they have 11 children, several divorces, nervous breakdowns, career scars and numerous million-selling records. Their one show Monday night at Wolf Trap launched a 33-week tour - another road show in four lifetimes of work, another string of hotel rooms and airports, unfamiliar dressing rooms and musicians.

"I love it," Whiting says. "People ask me, 'Why don't you retire?' Why should I? This is the best time. It's the women's time now. That's why this act is so successful. That we're all women and we're still working."

Music director Frank Ortega arrives at the dressing room door. "He's the greatest," Whiting says. They talk about how they can often gauge the audience by the overture, by which songs are recognized and applauded.

"They don't applaud my songs," says Whiting.

"That's just because they're played out of context," Ortega answers. "I do 'Moonlight in Vermont' sort of uptempo, and they don't recognize it."

The first time they did the show, September 1977 in Los Angeles, the order of each star's appearance was determined by tossing a coin. Traditionally, the opening spot is the least desirable, but now they're agreed on a set order: Whiting, O'Connell, intermission, Rose Marie, Clooney, and a group finale. "It seems to work best that way," Whiting said.

It was time to walk upstairs to the stage with Ortega. "Is this the moment of no return?" she said jovially. "Now that it's here I have these foolish fears . . . Let's go."

The audience is waiting. The musicians are waiting. Whiting is waiting. The audience starts clapping impatiently. "I hate it when they do that," she mutters. "What's wrong? Why are we late?" she asks the stage manager.

"The follow spots," he says. "Evidently one of them is hung up and they're trying to fix it."

Joe Schribman, the gravel-voiced, grey-haired manager, arrives. "What do you think of the house?" he's asked.

"Fantastic," he says, "are you kiddin' me? They're out on the lawn. Where the hell is your mike?" he asks Whiting. She tells him it's on the piano.

Schribman, who calls every female "sweetheart" or "dear," is new to the tour and had spent the previous days trying to find his stars as they flew in from various parts of the county (one with a cold), setting up rehearsals, making sure the stars were rested.

Rose Marie arrives in a pink cotton housecoat and white scuffies, smoking a cigarette and exuding perfume. "I love ya," she says to Whiting, and they kiss each other on the cheek. A few minutes later another lady arrives in a voluminous cotton housecoast and rollers. It's Rosemary Clooney. She and Rose Marie embrace and whisper something. The band has started the overture, and Whiting is clenching a wadded Kleenex.

"Oh, Turn that yellow off," she says to no one in particular, as a particularly vivid light goes on onstage.

"You look marvelous!" Clooney says to Whiting. "I love your dress." The three are huddled together in the wings, waiting for Whiting's cue. "And now; ladies and gentleman. . . ." She bounds onto the stage, grabs her microphone and sings:

"I want to laugh all of my laughter before I go . . ."

She segues into another song, and another, and then introduces the song written by her father, Richard Whiting, which became her first gold record, "My Ideal." For this she puts down the microphone and belts it out au naturel:

Will I ever find

The boy on my mind,

The one who is my ideal?

Maybe he's a dream,

And yet he may be,

Just around the corner waiting for me

A stagehand rushes backstage and hisses frantically at the stage manager, "Can someone get a message to her? She can't sing without a mike, she did a whole song with the mike on the piano! The people on the lawn are screaming!"

He is told a calm down, this was the only song she did without the microphone. He leaves.

A medley from the 1940s, when "there was a sense of togetherness we don't have now," and Whiting's half hour is over. She retires to her dressing room to read novels or magazines and await her cue for the group finale.

She can hear the rest of the show over the intercom - O'Connell's songs from the Big Band era and reminders of her years with Jimmy Dorsey's orchestra, Rose Marie's broad comedy, which the audience seems to adore, and Clooney's full-voiced renditions of old Hit Parade favorites and new love songs.

Clooney sings "The Promise," which, she tells the audience, she is going to sing at the September wedding of her son, Gabriel Ferrer, and Debby Boone, who has recorded the song. She's practicing the song now, she tells the crowd, so she won't cry when she sing it at the wedding. The audience loves it.

A stagehand knocks on Whiting's door and then hands her a pile of programs to autograph. "This one is for Mrs. (Jouett) Shouse, if you want to add a special message," he says.

"Oh, that's the lady that owns the place, right?"

For the last few years Whiting has been appearing in musical comedies - "Mame," "Gypsy," "Call Me Madam" - around the country and preparing a concert act, "Maggie and Friends." She keeps an apartment in New York and another near Hollywood and says she is content with her life. She has a 27-year-old daughter who's in the garment business in New York.

"I've always had a good time," she says, touching up her eyebrows with a light brown pencil. "So many people sit around dreaming about what they want to do. I get out and do it. I love to see new places, go to museums, the theater, shop. I love to work. I sing every day."

In their off hours, Rose Marie and O'Connell sometimes play Yahtzee, a game, or they go to movies or shopping.Various children drop in occassionally. The four give each other little presents before every opening in a new city. When tensions arise, Whiting says, it's usually Rose Marie who calls them together for a meeting to clear up "little misunderstandings."

"I never thought this would work," Whiting says. "Four women? But we know what makes each other tick. I know what these women have gone through. They're had problems and risen above them. We've all been through touring, the getting up early, schlepping the bags, getting out of the airport. Now we're four and we don't have to do it alone anymore. . . . Women can talk to each other the way men can't. You can talk about how your feet hurt, or your heart is broken, or whether this or that dress is all right. We're enjoying ourselves." CAPTION: Picture 1, Margaret Whiting in an early publicity pose; Picture 2, in her dressing room during current Wolf Trap engagement, by John McDonnell-The Washington Post; Picture 3, From left: Rosemary Clooney, Helen O'Connell, Margaret Whiting, Rose Marie