One night in Manhattan, after Ralph Lauren had become Ralph Lauren of the clothes with the little polo players galloping away from the torsos of spenders all over America (not to mention the cologne, the western look, the $250 Victorian blouses, mass-production authenticity), he was standing by a piano.

"I was singing, with the mike," he recalls now over coffee at the Fairfax Hotel. "It was at the house of Steve Ross, the head of Warner Communications. Woody Allen was there, Diane Keaton, John Fairbanks, some phenomenal people. We were all singing, it wasn't just me. We were singing Frank Sinatra songs, 'You Make Me Feel So Young', that stuff, when he walked in.

"Frank Sinatra walked in, and then he was standing next to me, singing, and I'd give him the mike, and he'd give me the mike, and I wanted to tell him that years before when I was like 16 in the Bronx and all my friends are listening to rock'n'roll, I'd defend him. And when I'd hear that Frank Sinatra might do a TV series, I'd want to yell tho him 'Don't do television! It'll ruin your image!'"

The image was integrity, authenticity, all those things that had beckoned and glimmered to Ralph Lifshitz, 16, living by the Mosholu Parkway, a short kid with a hint of a lisp and a right eye that wandered sometimes.

And a kid who was "very pure, very fanatic," a kid who "fell in love very easily," who read F. Scott Fitzgerald and knew what the writer meant by the white flannels blowing in the wind, who glided out of Cary Grant movies doing the Cary Grant ball-bearing walk.

When he was 16, it was a very good year. Along with his older sister and two older brothers, he changed his name from Lifshitz to Lauren. In that same year, 1955 -- in an era when Ivy League styles were power, grace and authenticity -- he took the subway into Manhattan one day.

"I went to a tailor and I had him make me a pair of Bermuda shorts out of tweed. With a little belt in the back." And he wore them with button-down shirts from Brooks Brothers, "the main floor, not the 346 shop."

Apotheosis! Avatar! "Everything hs to be perfect," as he says now at 40, walking out of the Fairfax toward Dupont Circle.

"I'm selling a way of life and dreams -- my own dreams. I didn't know what a fashion designer was. I'd never been to a polo game when I named the line, but I loved the ambience. When you grow up in the Bronx, you don't go to polo matches too much. Somebody said one time, they said I'm actually a writer who writes through clothes. I think that's absolutely right."

Strolling up Massachusetts Avenue, he keeps pausing to make his points in a gentle, friendly voice. It's his clothes that are puzzling. Why in Washington, the glen-plaid worsted capital of the world, has he chosen to wear a pin-striped double-breasted suit with lapels cantilevering all the way to the armholes? Especially when he says he likes the way Washington men dress?

Well, he does and he doesn't. He's here for the opening of Polo store on Connecticut Avenue, with windows full of the sort of go-to-hell pastels that you see at Fourth of July cocktail parties in Edgartown. But in Washington, where establishment style seems to be set by midwewestern lawyers, his clothes look a touch daring on both ends of the formality spectrum.

He's on the high side, himself, settling pin-striped onto a bench in Dupont Circle.

"John Kennedy had style. Franklin Roosevelt had style, John Lodge had style."

The Washington image! Just as he wants to force the Ivy Leaguers to hew closer to their F. Scott Fitzgerald heritage (there is no zealot like a convert after all) he has put himself into clothes appropriate for, say, signing a peace treaty. Integrity. Authenticity. The dream!

"Usually when I travel I wear jeans and cowboy boots, but that didn't seem right for Washington. I had no desire to wear them here. I wanted to be more traditional."

His whole state of being can depend on it. "When I wear cowboy boots, I have a different look and a different manner. Now, dressed like this, I'm smoother . . . ."

The lawyers lope across the circle pants cuffed an inch above their shoes. They are pointed out as Washingtonians who no doubt think of themselves as snappy dressers. Says Lauren. "No style."

Then: "Nice Tie!" he shouts. The owner turns. He is wearing an old Polo tie with the polo player galloping out of his navel.

"I believe I recognize you," says the man a black psychiatrist named Walter Presnell. He also wears a blue blazer, tan slacks and a diamond stud in his left earlobe.

"I'm very fond of your clothes," says Presnell. "They're beautifully done."

Lauren gets recognized all over America since he took to modeling his own clothes. "People stop me on the street -- they feel a camaraderie."

Charles Cole, the makeup man at Elizabeth Arden, comes by in a pink Polo sweater to say hello. As does Paula Kerr, of Fall River, Mass. Lauren looks her up and down.

"You look just like Diane Keaton!" he deeps saying, and it's a compliment. After all, Lauren himself will confess to a small urge to be an actor, and he enjoys the fame.

It's pointed out that Barbra Streisand once said she didn't aspire to be a movie star when she was young -- she wanted to be the people in the movies.

"That's it! That's exactly right!" Lauren says.

It's been a long way since 1966, when Lauren used to drive out to men's stores on Long Island in his cream-colored Morgan with the leather strap across the hood, and try to sell his wide ties.

He paid his dues -- City College of New York at night while he clerked. at Brooks Brothers during the day. Then he worked around the industry as buyer and salesman until he talked the Beau Brummel necktie company into making up his Polo ties.

In two years, American wastebaskets were full of the narrow ones, and Lauren ws launched into a business that he says will gross between $90 million and $120 million this year. He has a duplex on Fifth Avenue and a summer place in East Hampton. He has a wife and three children.

His fashion empire has spread to clothing for men, women and boys (little blue blazers, naturally) perfumes for men and women, luggage, sports clothes and cowboy gear from boots to hats. It's clothing that tempts you to pretend to be who you think you really are, while simultaneously claiming total authenticity.

"When I went to Dallas I tried to buy a fringed leather jacket, and I found out they didn't have them in Texas. So I had to do it for them."

His image of western wear was reality -- was it his fault if Texans didn't really dress that way?

The thing is, he's desinging clothes for people who don't want to look like anyone designed their clothes; he is self-consciously unself-conscious. But then, isn't anyone who dresses well? And don't they hate to have it pointed out to them?

Lauren sighs. "Paul Simon is a friend of mine. He doesn't worry what he wears, he doesn't want to look like clothes at all. He comes up to my office. I just wear jeans and old flannel shirts up there, and he says: 'You always look perfect.' I can't take it as a compliment, but what can I do? You shouldn't deny taste."

Image and reality: Ralph Lauren and Frank Sinatra handing the mike back and forth, or Cary Grant . . .

Walking down Connecticut Avenue to inspect the 15th Polo Store he's opened, Lauren tells his Cary Grant story -- how he'd been designing ties to look like Cary Grant would wear them, "and one day Cary Grant called me and said he'd been wearing my ties for years."

How much authenticity and integrity could you ask for? Ralph Lauren had done it both his way and Cary Grant's! The problem being, as Lauren seems gently pleased to point out, as he nears the store awning: "Cary Grant once said: 'Even I wish I were Cary Grant.'"

And doesn't that put Ralph Lauren, tweed Bermudas and all, into Cary Grant's league?