"Michael Tippett stands as a giant on our musical horizon. He virtually alone among contemporary composers, has dealt forthrightly with the central issues of our times. He has forged a musical-theatrical language which will transmit to future times spiritual and human concerns wich our times have confronted. His operas form perhaps our most eloquent and elegant musical bequest." -- Sarah Caldwell

SIR Michael Tippett, who came to town last week to rehearse his Fourth Symphony, and to conduct it with the National Symphony tonight at Wolf Trap, is England's leading composer. Yet his music has taken longer to become known in this country than that of the late Benjamin Britten.

Part of the reason is that until he was around 30, the composer, who has always been highly self-critical, destroyed all hs compositions. Another factor is the stylistic complexity that provides Tippett's music with its central power. It is a very different style from, say, that of Britten, many of whose operas and other large works have long been staples in this country.

So far only one of Tippett's four operas, "The Ice Break," has had a professional production in this country. That came last year from Sarah Caldwell and the Opera Company of Boston. ("The Knot Garden" was given a student production at Northwestern University in Evanston, Ill., around the same time and it won warm commendation from the composer.) "Now Sarah wants to do all four operas," Tippett said last week. "She has applied to my publishers here for a hold for them. And she gave an impression that she would bring 'Ice Break' back again this coming season. I admire her immensely. I get on very well with her. I thought the 'Ice Break' in Boston was marvelous, a very good production. Such vitality!"

That Caldwell returns Tippett's admiration is obvious from the fact that the composer-conductor is appearing with the National Symphony at Wolf Trap in Caldwell's first season there as music director.

Sir Michael Tippett was 75 on the second day of this year. But he does not look anywhere near his age. Nor, as he talks about it, does he sound it. Stretched out last week on a bed in his motel room near Wolf Trap, Tippett said, "I hardly ever sit. I have a lot of problems with stomach muscles, and an old doctor told me, 'Don't sit unless you have to. You don't want to spend all your life sitting at a desk.'"

He explained that he has cut back on his conducting these days. "I have a slight heart condition -- it's not serious," was the way he described it. "But in Dallas I had to go into the hospital. It comes from putting pressure on both the composition and the conducting so I only conduct absolutely very rarely, when I want to."

With equal nonchalance, he spoke of another problem: "It's my eyesight, which is going off periphery sight but not central vision. Oddly enough it's very like what the aged Rubinstein has -- you can't go blind, but you can't focus -- and the light makes a lot of difference."

He talked about the relatively late fame of his compositions: "They needed younger conductors. The older generation -- Boult, Sargent, Beecham -- they did not know Monteverdian polyphony, the contrapuntal style. Sargent and I went to the same grammar school 10 years apart. He disliked my music, thought we were getting too intellectual, too tough, too something or other. To be quite honest, Boult, whom I knew very well, he didn't find the music easy. It wasn't the modernity of it, it was to do with the polyphonic element. They'd never seen Monteverdi, never looked at those pieces at all. So this element which produced a different kind of strength was quite unfamiliar to them.

"One had to wait until a younger generation came along. It was also a matter of technical bating. One only has to beat a very light beat, because it's only metrical, it's not a pulse beating. They hadn't got these techniques."

Tippett discussed the Fourth Symphony, the one he is conducting here. It was commissioned by the Chicago Symphony Orchestra and given its premiere by them a season ago. "[Sir George] Solti in Chicago was something quite surprising. He was most accurate, he knew the score inside and out. He did it later in London with a London orchestra, and afterwards he said to me, 'Now I know what it is,' I have conducted it only in Australia with the Adelaide Orchestra, wonderful young players."

"It's a very virtuoso piece, sort of a show-off, but that's not what it's about. There are some very tricky things and hard work for the strings, and more from the brass. They'll find their way. We'll see if we can get it as good as we can."

Tippett said he has finished a work hat "hasn't been performed yet. It is a concerto for violin, viola and cello. I don't think there is any other concerto for these three. A triple concerto like this would be like an addition to the Brahms Double. It has its own problems -- you can't triple everythng . It is due to come out with the San Francisco Symphony in August in the Promenade Concerts, but with a strike out there all is in question. It may have its first North American performance in Toronto in October with Andrew Davis.

"I haven't heard it yet. It's a very romantic work. It's simply not a symphony, not a concertante piece, it's a real concerto with the polyphony of the three instruments and their diversity as I write them. There's a great deal of sound there."

For the future, this man who has lived through three-quarters of the century is still composing. "It's a concert piece for singers and instruments for a part of the Boston Symphony centenary. It's a long time off, I think it will be for the '82-'83 season. It will take 2 1/2 years to write. It's to sort of a composite text of my own. I think they will put it somewhere in the spring and then it to Tanglewood. It's not the Ozawa kind of piece, obviously. It's Colin Davis [the Boston Symphony's principal guest conductor]. They're going to preceed it by doing all four of the symphonies, which is very nice."