LIVINGSTON BIDDLE, who is the new chairman of the National Endowment for the Arts, wraps rubber bands around the stems of his eyeglasses. It helps keep them on. His neckle is wrinkled, his brown, narrow-lapelled suit is dandruff-sprinkled, his shirt is white-on-white, with the collar points heading for flight. Gray regimental moustache. Sideburns which meander down his jawbone. No crisp Mr. I'm-Awake-So-You-Can-Sleep. Not your average high-ranking appointive politician.

"The idea of public service was instilled in me in my youth," Biddle says. "I was taught that if you're given a privilege you must return it."

Biddle is sitting - one is tempted to say relaxing, but that's the way he always looks - in the office he assumed in November as the new chairman of the National Endowment for the Arts. He presides over a $115 million budget, a fast rise since the original $2.5 million in 1966. Plus a view of both the Watergate and the Kennedy Center, "the best view in Washington," he says, with the jets lifting soundless over the bend in the Potomac, gulls in the sunset.

Biddle is explaining away the flap that surrounded his appointment. And such a lovely little flap it was.It first reached the rude gaze of the public on August 17, in a Wall Street Journal editorial, Livingston L. Biddle Jr. had sung a song, said the Journal, which seemed to warn that the National Endowment for the Arts was about to fall into an orgy of pork-barreling.

"I was representing Senator Pell - I was still working for him then - at a meeting of the American Association of University Presses," Biddle says. His Philadelphia accent bends the vowels around, a sound reminiscent of someone springing sheet metal. "At the end of my speech I sang a song." He offers a slow smile. "I have a terrible voice but no inhibitions whatsoever. It was put to the tune of 'Friendship.' You know, that old Ethel Merman Bert Lahr number. One of the lines was: "If you ever need Senator Pell, ring our bell.' A reporter there got it wrong, and it came out: "If you ever need a grant, call on Pell. if you ever need a subsidy, ring my bell."

Misquoted or not, it was a song, after all, and hardly seemed a manifesto. But in September, as Beddle awaited Senate confirmation, the New Republic took the Journal's wryness and flogged it into high dudgeon. Even if the song were a joke, TNR said, it "would mean that he is merely tasteless, not crooked. In either case, Carter could not make a worse appointment if he tried."

On October 12, the New York Times joined the cry by publishing an interview with Michael Straight, acting chairman of the endowment. Straight said: "If the appointment of the staff director of the Pell oversight committee isn't "political," what is? . . . It's true that Liv Biddle helped write the legislation that set up the endowment; he's good, decent man who'll be a conscientious chairman. But why didn't they look for someone of national stature who'd be known and respected by both political parties?"

The next weekend, the Times trundled out the big guns with art critic Hilton Kramer paraphrasing Marx, oddly enough, to express his fears that the endowment was getting "populist." Kramer wrote: "A specter is hauntin the arts and the humanities in the United States today . . ."

Biddle's appointment sailed through the Senate, of course.

"All that rhetoric had been used in the fight between Senator Pell and Ronald Berman at the humanities endowment last year," Biddle says. "It was a vocabulary looking for a target. We're going to have contention in the arts world forever. I don't know the other worlds that well, but any fields that deals with self-expression and individuality - and this is what the arts do in a democratic society - well, these individuals tend to be contentious."

But a specter! Then again it's hard to imagine any Biddle as a populist, eihter. It's a notion which Biddle might find extremely flattering.

Biddle is one of the Philadelphia Biddles.They go back to William Biddle, who was imprisoned with William Penn in England. This is the Philadelphia equivalent of having been on the Long March with Mao. Nicholas Biddle founded the Second Bank of the United States and battled with Andrew Jackson. Francis Biddle was attorney general under FDR. They're tied up with the Dukes, as in Angier Biddle Duke, and the Drexels and with each other. "Some Biddles wouldn't think of marrying anyone but another Biddle," says Biddle, easing into his smile.

Biddle, 59, was a classmate of Pell at both St. George's School and Princceton. On graduation in 1940, Biddle became a copyboy, then head copyboy, then reporter at the Philadelphia Bulletin. In 1942 every branch of the Armed Forces turned him down for bad eyesight. He joined the American Field Service and drove an ambulance in North Africa, Italy, France and Germany, winning decorations, and experience of a range of humanity Biddles don't always run into. "I began to see the Pre-war Liv Biddle as a limited human being," he says.

In 1946, "I found a house in Vermont where Rudolph Serkin had worked on his music. People told me I used the same desk," Biddle says. "I wrote a novel about Chicago. I'd never been to Chicago. I figured that if Robert Louis Stevenson could write about places he'd never been, so could I. It was a disaster. So I enrolled in Martha Foley's course at Columbia. I wrote a short, called 'First Tarpon,' about a hotel in Florida where we used to spend winters. She published it in a collection, and I knew I could be a writer."

Biddle wrote four novels, two of them best sellers, with one, A Village Beyond, selling 300,000 copies. All are set in the Main Line of Philadelphia, a rich old string of suburbs including Bryn Mawr, where Biddle grew up in a house named Westview. "I wouldn't say they were great literature," he says, "but I like to think there are parts . . ." Biddle, who majored in the French and English novel at Princeton, says he intended them as "a critique on my home environment," and an attempt to increase the social responsiveness of the world he grew up in. He was considered "an eccentric Biddle" for his pains, he says.

We leave Biddle's office at six, to drice to his house in Georgetown. In the elevator, a fellow passenger learns he's riding with the new chairman of the endowment.

"This place is so incredible!" the man exclaims. "You must be very proud, knowing the good that it does."

"Well good, I'm glad, yes," Biddle says, in his odd mix of shambling and self-assurance.

Even after eleven years, it's hard to conceive of the government of the United States giving away $115 million every year to sculptors, composers, poets, ballet companies, egg painters, Indian powwow dancers, symphonies, a toy and doll museum, a fiddlers' contest and so on, in whatever strikes the fancies of the enddowment boards and the state arts councils. (Biddle hopes to raise this figure to $200 million.) The thought of the endowment strikes giddiness in hearts of curators and fund-raisers. The rush of applications has finally turned the endowment into one more bureaucracy, some endowment staffers complain, with none of the we-brave-few feeling of the early years, under Roger Stevens, and then Nancy Hanks. Hanks, of course, was one of the great appointive politicians of her time, famous for her ability to play favorite granddaughter to the old curmudgeons of Congress. Some worries that she could become an unchallengeable institution, like J. Edgar Hoover, until she announced she was not a candidate for reappointment. In any case, she is a tough act to some arts and endowment people as a consolidator of gains, rather than an innovator. He has said that he wants three deputies to make the aesthetic decisions while he works on administration.

Again, he hardly looks the part; one almost looks for inkstains on his fingers. But then, unlike most of us, Biddle never has to worry about proving his class. His car, for instance, is a Volkswagen Rabbit, in which he has left the radio playing all day, we discover when we climb in. He wrestles apologetically with the steering wheel lock. He pays the booth attendant out of a wallet thick with stray slips of paper.

"I'd been looking for a job in Washington while I wrote," he says, as we pull onto the Whitehurst Freeway. "One thing that persuaded me was a remark my daughter made one day in school. All the students had to say where fathers worked, and describe their offices. A student would stand up and say, 'My father's a lawyer, and he works downtown in a big office . . .' Or a doctor in a professional building. Then it was my daughter's turn, and she couldn't think of what to say. Finally, she just said: 'My father works in the attic.' I did, you see, in the third floor of our house in Philadelphia. When I heard about it, I thought yes, I'm not in the world enough,"

Biddle then ran into his old school pal, Claiborne Pell, at da cocktail party, and came to work for him in 1963. In the late Sixties he went to Fordham University to develop an arts program at New York City's Lincoln Center. In 1971 and 1972 he was chairman ofthe Pennsylvania Ballet Company, in Philadelphia, before returning to Senator Pell's office.

Biddle lives in a brick Federal house on P Street amid the glorious hand-me-downs of acquisitive ancestors, the leading one being his father. His Dutch wife, Catherina, whom he married after his second wife - mother of his two children. Cordelia and Livingston IV - died of cancer in 1972, leads a tour of he oil paintings, set among the Roman heads, the ivories an prayer rugs, Chinese chest and statuette of samurai, vases and a miniature replica of Czar Alexander's troika, given, it turns out, by the czar himself.

"Look at this," Biddle exclaims. "My father left it to me." It's an album, some kind of logbook it appears as he opens it with an eager flair, as if a cloth snake might pop out of it. "Look," he says, pointing to a signature. It takes a second.

"Czar Alexander?"

"That's right. This was the logbook of my father's vacht. He and my uncle went all over the world in it, collecting a lot of this furniture, these rugs. He showed it to me one day, and I said 'You mean the czar came on board? Dad said 'Yeah, he was a nice guy. We gave him lunch.'"

The yacht, named the Alcedo, was a 275-foot screw barkentime. The Germans torpedoed it in World War I.

This sort of heritage "tends to both strengthenand limit," Biddle says. The strenght is in the tradition, but the limitations, well, "some people think that the traditions are all there is. I heard a woman say about her debut that it was the greatest moment of her life," he says with a mild but firm astonishment. And when it is suggested that he does not match the stereotypical appearance of a man in his position, Biddle's tone, that soft voice patting through his nose, implies that this too is an examined choice: "Some people need to put on masks."

If he has one, it's invisibility. As far as his role as leader at the endowment goes, we can expect semething far less public than Nancy Hanks. "I think that stress needs to be placed on the endowment for the arts, not on an individual."

I recall the convening of the National Council on the Arts the previous Friday, in the Presidental Room at the Mayflower Hotel. Florence Lowe, the public relations woman who is widely credited with the creation of Hanks-as-heroine, button-holes Biddle as he wanders inot the room to tell him about a dinner in New York the night before. "It was a lovely dinner but they didn't caonize the guest of honor," she says. Nancy Hanks was the guest of honor, it turns out, and Lowe is acutely sensitive to the personal and political implications. "They didn't canonize the guest of honor," she says again.

"Yes," Biddle says. He looks like he's trying to remember whether or not he left his keys in his car. "Yes," he says again, and strolls away, a man no one could ever pick out in a crowd.