"Ooooh! We are to play on that?"

Alexander Schneider, the great violinist, gazed dubiously up at the rickety stage in the Kennedy Center film theater.

Oh no, he was told, this was just for the radio talk show. The concert would be in the center's new hall.

"I hate being so high," he muttered. "Once I had to play a Schubert quintet on a thing like that, and we shook every time we did a fortissimo."

He showed how they shook, setting off his colleague violinist Jaime Laredo, on a hair-raising account of the stage in Glasgow, Scotland.

And then there was the time the 70-year-old Schneider thought his stool was behind him in rehearsal at the Curtis Institute and fell flat on his back. "But Isaac Stern, now, he likes it. He stands right out there on the edge of the stage and leans over the pit...."

Life on the road is just one damn thing after another, the prophet said.Even a traveling legend like Schneider -- veteran of the Budapest Quartet, pupil and friend of Pablo Casals, founder of orchestras, conductor, entertainer of presidents and missionary to the world for the cause of chamber music -- even he must cope with its slings and arrows.

Last month, arriving in New York exhausted and sleepless after a night on the Montreal sleeper, Schneider left his $250,000 Guarneri violin in a taxi. It was picked up by a Jazz trumpeter, Butch Cheatham, who for some reason kept it nearly three weeks despite the worldwide clamor.

"It's part of my body, part of my soul," Schneider said. "I've had it 29 years, and you can't buy them, you know. Stradivarius made hundreds of fiddles, but there are only 78 Guarneris."

Finally, the trumpeter contacted the frantic violinist, whose name of course was inscribed in the case, and claimed his reward of $13,500. He said he had never heard of Alexander Schneider.

Meanwhile, Isaac Stern had loaned Schneider his Guarneri copy. "And do you know, I was amazed. I thought it would sound different, but it was the same. Everyone told me I sounded just the same. But you can tell it's not the same instrument you've spent all those years with."

He had just finished his morning practice, 45 minutes of scales, had taken his morning stroll, and now was ready for the interviews and talk shows and lunches and rehearsals and whatever else came between him and the concert.

All his life has been devoted to music. His father, an amateur flutist in Vilna, insisted on it, which is probably why both Alexander (Sascha) and his brother Mischa are renowned violinists. (There is an unmusical brother in Toronto. Their sister and mother died in Dachau.) It seems almost an obsession.

"As long as I'm alive I want to help young people in music," he said. For years, he has given up his Christmas vacation to put together his New York String Orchestra, a group of talented student musicians who perform over the holidays.

He is a director of the famed Interlochen music camp and has appeared season after season at the extraordinary summer musical happening at Marlboro, Vt. And there was the Casalas festival. And the Israel festival. And the Schneider Quartet. And the Mozart festivals and Bach festivals and outdoor concerts and midnight chorales and the Sonata Ensemble...

"But I am taking a little rest this summer," he confessed. "It ma going to my place in Provence and enjoy the sun and the good food and the good wine. I love to cook, I am a very good cook, and I love good wine."

Perhaps it is that the future interests him less than it used to, that he is more content with the present. He doesn't go out of his way to learn the latest violin compositions, though he does keep up with new music for his conducting. He finds the world is full of people he doesn't understand.

"Today everyone is thinking of himself, only of himself. In the arts, in human relations, in everything.In music, they think only of technique."

As for himself, he is satisfied to have simply "enough" technique to play the way he wants. He is not interested in technical perfection.

"You have to feel," he said. "You have to show what you feel in the way you play, because there are things that no words can express, not even poetry. Casals used to tell me that. You've got to show it. But first, you must feel."