It is doubtful that any flutist since Frederick the Great has commanded such a following as Jean-Pierre Louis Rampal, who celebrates his 60th birthday here today.

And if the Prussian monarch had an edge in worldly clout, the Frenchman Rampal, by comparison, may well have the edge in numbers among his legions of admirers.

Among them is the National Symphony's Mstislav Rostropovich, who is staging a birthday fete here, billed as "Rampal's Diamond Jubilee," for his longtime friend -- much like earlier events with which the conductor ushered in the 60th birthdays of Leonard Bernstein and Isaac Stern. There are four concerts at the Kennedy Center and a black-tie birthday party tonight at the Watergate, to be followed over the weekend by recording sessions in New York with Rostropovich and Stern.

Rampal's fame probably has outdistanced that of either of those colleagues. Just consider the Billboard charts, the ones that separate the stars from the superstars. Rampal's most famous disc, Claude Bolling's Suite for Flute and Jazz Piano, is now in No. 5 position. It has been on the list for 310 consecutive weeks. That's roughly six years -- more than twice as long as its nearest competitor on the classical list, fellow flutist James Galway's "Annie's Song." CBS won't say how many copies of the suite have been sold, except to volunteer that it's "well over 500,000." Sixty-seven Rampal singles and sets are now listed in the catalog. Sales apparently are unharmed by his appearances with the Muppets and his standing invitation to return to the Johnny Carson show.

Rampal raised the flute from its relative parity with other woodwind instruments, piquing popular interest in the pure, elegant and almost fragile instrument that goes back at least to the god Pan. In the process, he provoked the most important instrumental revival since Segovia and the guitar.

In an interview this week Rampal, an exceedingly robust man now in the 41st year of his professional career and looking considerably younger than 60, disclaimed any such intent.

"I never even thought of it like that in my head," he said. "I don't know that I wanted to be the first. That is just not the way that it is done. Never. What we try to do is to do our best. Only in sports can you say, maybe, 'I am the first.'

"I am always very surprised about the size of the audiences when I go for the first time to a country. Though there are not so many places left where I can now go for the first time. But still, my wife and I were in Korea last summer on our way to Japan and the hall in Seoul had 4,000 seats, and it was already sold out when we arrived for all performances. Now, this May my wife and I go to China for the first time and we hope it will be the same."

Rampal took note of the built-in conflict created by the acoustical requirements of small instruments such as the flute and the need to accommodate their huge audiences. "Those halls are not the best for anybody, even a pianist, because if we play to a 4,000 capacity, we try to play to the last row. But if you are back there, how can you listen very carefully to what they are really doing . . . the nuances? It's a mistake, but we cannot change it.

"You speak about Segovia. He never had a big sound and never wanted to have a big sound, and the guitar is probably the most feeble instrument in the world to hear. And yet because of his stature and his reputation he is condemned to play in 4,000-seat halls, most of the time. It is very strange."

Yet as you sit in the Kennedy Center Concert Hall listening to Rampal and the orchestra rehearse the Khachaturian/Rampal flute concerto (a transcription, at the composer's suggestion, of his violin concerto), nothing seems very feeble there.

Part of the impression is visual. Rampal is a vibrant man of 6 feet 1 inch. He has the chest of a pro lineman, the slight paunch of a retired pro lineman, and his brown hair is beginning to go. The sound of his gold flute is hardly feeble -- perhaps not so rich in tone as the violin, but improving on that in agility.

One of Rampal's contributions has been to introduce into the flute repertory some larger-scale works, like the Khachaturian transcription. "I think that it's a good addition to the flute literature, because unfortunately we were out of a big concerto in this style of music. I would say that it is our equivalent of the Tchaikovsky violin concerto. It may be too kind to compare this work with the Tchaikovsky, but surely Khachaturian would not mind."

Perhaps Rampal's single most substantial contribution has been his role in reviving, through records especially, the baroque repertory for flute. "I think that I started with the baroque," he said, "simply because when the war World War II was finished it was time for people to like some music that was very well-made, and baroque is quiet music for the mind. And it was very popular because of that, because it produced balance in the mind."

Talking about nonmusical life, Rampal volunteered that he loves fine food and has never cared for football. "Tennis or swimming are for me. Oh, tennis, I would have liked to be . . . But I just play. My son plays well," and he pointed to his wife, Franc,oise-Anne, who was seated across the room: "My wife too, she is not bad," in a tone suggesting that Mme. Rampal beats him from time to time at their summer home in Corsica.

He added that he fails to get enough exercise to control his weight. And he kept fidgeting on a dainty Victorian love seat in the concert hall's Green Room and, finally, unable to get comfortable, declared, "This is dangerous. My weight. My weight," transferring to a sturdy black leather stool at the grand piano.

When it was time to go, Rampal stood up from the piano bench and held Mme. Rampal's fur, of Canadian fox, for her. A visitor reached over on the sofa to pick up Rampal's huge dark coat. Is this fur, too? he was asked. "Oh yes, it is mink, you see. But it is hard to tell. They tell me that I should wear the back pelts of the mink, because if I wore the tails someone might think I look effeminate." Both Rampals uttered deep roars, and departed for a late lunch.