Lunch time. Rehearsal is over in the Kennedy Center Concert Hall, and Eugene Fodor has fiddled so well that the violinists of the National Symphony are talking about it back-stage in hushed voices: "He really had it, today . . . What a pair of hands! . . . He sounds like that concerto was written for him."

Orchestral violinists are not given to hero worship, and one would think that Fodor has no problems at all. At the moment he has three, but only one is serious: His G string is squeaking. The shortage of baby sitters at the Watergate Hotel and his need for a haircut are secondary.

"I'll have to put you off for a while," he tell a visitor. "I have an emergency with my bow, and I have to go across town to 13th and G."

There are only a few violin technicians in the country who are allowed to put new hair on Fodor's bow; one of them, Jack Weaver, has a shop downtown.

"I'm playing the Khachaturian this week," Fodor says in the car en route to Weaver's shop. "My concerto repertoire for this season also includes the Men delssohn, Brahms, Sibelius, Paganini one and two, Glazunov and Tchaikovsky. I can play any one of those concertos tonight."

Sometimes he has to be ready to: "I was in Charlotte a while ago, on stage with the orchestra and ready to play the Mendelssohn, when I heard the opening bars: Da-da-dum . . ." and he begins to hum the bouncy beginning of the Khachaturian. "I had to make a quick mental readjustment, but it worked out all right. The same thing happened to me with the same concertos in Santa Barbara, but not in the same year."

The car passes the White House on the way to the violin shop and stirs up Fodor's memories. "I've played in there. I was the first musician President Ford asked to perform in the East Room." He may expect an encore invitation from the new administration. Back in Colorado, where he was born 31 years ago, his father-in-law was the state chairman of the Reagan for President committee in 1976.

He wasn't his father-in-law then; Fodor has been married for three years and seems to be settling down after establishing a reputation earlier as an enfant terrible. When he opens his violin case, there are three pictures in it, as well as two violins and four bows. One is his wife, Susan; the second is his daughter, Daniella; the third, Niccolo ypaganini. "My three loves," he says, smiling fondly.

Paganini is one of the key figures in his life, not only because he frequently plays Paganini's music, but because winning the Paganini's music, but because winning the Paganini Competition in Genoa in 1972 launched him on an international career. "That was what really got me started," he says. "Winning the Tchaikovsky Competition speeded things up; in the next three years, I played in every one of the 50 states, and by now I have played on five continents and with nearly every major orchestra. But that was on the way. Without the Tchaikovsky, it would have taken me two or three years longer to get the same engagements."

Since his rise to the international superstar level, Fodor has received mixed reviews, with critics often more enthusiastic about his technique than his musicianship. He believes the two are not contradictory but "intertwined" and he makes a point of studying negative reviews. "About once in 100 times, they are actually helpful," he says.

Fodor's ambiguous victory in the 1974 Tchaikovsky Competition in Moscow is one of the musical question marks of the '70s. In a very curious decision, the judges declared that none of the violinists that year was up to first-prize standards and instead gave three second prizes -- to Fodor and two Russian violinists. Fodor questions the verdict. "I was told by some conservatory professors, in private, that the judges were instructed not to give a gold medal to anyone but a Russian," he says, "and I believe the standard that year was very high. They had more competitors who had already won other major competitions than any previous Tchaikovsky Competition. They couldn't give me a gold medal because they were under orders, and they couldn't give it to anyone else and not to me because the audience was so solidly behind me."

He had not planned to enter the Tchaikovsky Competition, but one of the judges from the Paganini Competition had written to tell him he should. "He told me, 'You play like a Russian,'" Fodor recalls. Naturally. Fodor's ancestry is Hungarian (he is the second generation of his family born in the United States), but the two violinists who were his ideals were both born in Russia: David Oistrakh and Jascha Heifetz. He studied with Heifetz for a year, when he was 20, and still speaks of him with admiration ("I learned more in that one year than the previous seven"), but the parting was not amicable. The musical grapevine says that Heifetz expelled Fodor for not conforming to his rather strict dress code in classes. Fodor complains about Heifetz's attitude on student concertizing.

"Toward the end," he says, "I began doing more and more concerts, and I finally left the class. Heifetz wouldn't let me perform while I was taking his class. Conductors would ask me to play, and I would ask him. 'Certainly not,' he would say, and the next thing I knew one of his former students would be playing instead of me."

In Weaver's Violin Shop, on the fourth floor over Campbell's music store, a schoolboy, in with his mother to buy a new violin, recognizes Fodor and asks for his autograph. Fodor signs quickly and resumes his conversation with proprietor Jack Weaver; "'d like a little less hair," he says, taking an 18th-century bow from his case. "Maybe you can take the hair from this one" (out comes another 18th-century bow). "It's nicely broken in."

Weaver tries a quick cadenza on the sometimes squeaky bottom string -- now no longer squeaky. "It sounds all right to me; what kind of G string are you using?" Weaver's son, Bill, joins in; he favors rehairing immediately, while his father wants to wait. "It still bites," says the elder Weaver.

Finally, the decision is made to wait a day; new hair will have to be broken in -- several hours of work which Fodor would rather postpone. "I'm playing the Khachaturian, and it tends to tire your left hand after a while," he says.

Over lunch, he talks about running and smoking; he began the former 10 years ago to quit the latter and recommends it. He turns down a glass of white wine (the hands must be steady), but eats his fish (ceviche as hors d'oeuvre; smoked salmon in the main course) with relish. "I have to be careful about food on a day I'm performing," he says. Martin Feinstein wanders by from an adjoining table. "Merde for tonight," he says -- a traditional good-luck wish among French performing artists.

Fodor smiles and returns to family reminiscences. "I was born into a musical family; my great-great-grandfather founded the Fodor Conservatory in Hungary, and my father is the only one in generations who has not been a professional musician. He plays the violin as an avocation; ruined his hands playing handball."

Lunch ended, the only major priority is a haircut. At Raymond's Place for Hair in Arlington, he echoes a theme heard earlier at Weaver's: "I want a little less hair." Raymond, like Weaver a technician recognizing another technician, gets quickly into the minutiae and soon Fodor, still damp from a shampoo, is sitting amid the other customers (predominantly suburban housewives) discussing his plans. "Next week I go to Korea -- one performance in a hall that seats 5,000 -- and I'll stay around probably for a few days. Then I play in Las Vegas, and after that a benefit at the governor's mansion in Phoenix. He is booked ahead for two years and is particularly looking forward to Paganini's 200th birthday, Oct. 22, 1982, when he still be playing Paganini's music at the world fair in Knoxville with the Concertgebouw Orchestra.

"Things are poping," he says. "I can only spend five weeks at home each year, but fortunately my family can travel with me. It's getting so I don't have time to record what I want to." What he wants to record next is Vivaldi's "Four Seasons."

A day later, both hair problems have been solved; the bow has gone back to Weaver's, and the new hair, already broken in, is "digging in like a steam shovel," Fodor reports. Lacking a Watergate baby sitter, he has managed to get one through a friend who is in Congress. And he knows what concerto he will be playing next -- at least for the rest of this week.