Asking Isaac Stern about playing the violin is like asking Jack Nicklaus about playing golf. You are getting answers from the very top. The first thing Stern said the other morning, right after finishing a strenuous rehearsal of the Tchaikovsky Concerto was "I don't care what else you write, but I want you to say that I have taken off nearly 30 pounds." (There's another parallel with Nicklaus.)

All The Things You Have Always Wanted to Know about the Violin and Been Afraid to Ask: Why, for openers, do violinists always stand slightly behind the pianist, and several feet nearer to the audience?

"It's for acoustic reasons," Stern began. "If you stand in front of the piano, it's impossible to tell about the balance. All that noise behind you is too much.

"The violinist stands so that he can have eye contact - he can see the pianist's hands and the pianist can see his bowing." With a Stern chuckle, he added, "You always judge the ego of a violinist by the distance he stands from the piano."

Listening to Isaac Stern playing the violin conjures up visions of a child prodigy tossing off dazzling passages at the age of 5. Only it was not like that with the young Isaac. "I did not want to learn to play by any standard system of any school," he said. "I started when I was 8 and worked at the violin for about four years before I went to Naoum Blinder in San Francisco. I developed a very personal relationship with him. He was a violinist of great quality and also an instinctive player. He allowed me, helped me to learn how to teach myself. I never did the usual preparatory scales, etudes, and so on. Somehow my hands fell into place naturally. I used the difficulties in in the pieces I was working on as exercises.

"You see, of you practice exercises and etudes and so on, a kind of routine sets in the hand. For me, the weakness of this method is musical: A pattern grows so that when you come to a scale or passage that you learned in an exercise, your hand immediately plays that passage the way you learned in the etude."

After a moment, Stern went on. "I rarely play the same scale the same way in different pieces.It depends on which string you are playing on, where the key point of the scale is. The fingering you are using must allow for the full flow of the music."

There is a natural curiosity about musicians who have a lifetime acquaintance with the great works for their instrument: Do they change their views on them over the years? For Stern, this would mean that Beethoven, Brahms, Mendelssohn, Tchaikovsky, and Mozart concertos.

"I don't change my views of them consciously. The changes germinate. I had not played the Tchaikovsky Concerto for about eight or ten years. It had become a block for me. Then I decided to take it out of mothballs, take it all apart, put it together again. Actually I found that in a week or so it all fell into place. And I'm playing with it. I'm having fun with it. There's not just one way to play it."

During the rehearsal that morning, the fun going on between Stern and Rostropovich was apparent. So was something else. Stern's habit of talking to the orchestral musicians while he is rehearsing. He says about that. "I do it with every orchestra. I can't help it. I'm driven by what I hear. If I hear something that's wrong, I have to say something." At one point in the rehearsal he had turn to the violins to say, "Not louder, just clearer."

You might think that for Isaac Stern, there would be no technical hurdles, but he says there are. After some deliberation, he names one: "A kind of mechanical accuracy in their velocity. The Paganini things." But he does not plan to work on them. There are works he has never played that he does plan to play. "The Schoenberg Phantasy and the Ysaye sonatas," Stern says, naming mountains in the violin range he still plans to climb.

He has strong opinions about what is important in making music. "It's always between the notes you have make the music. The trouble with the Tchaikovsky is that there are so many notes. Some of the passages are horargrhghrghh, hgadadhgdahdgahdahgda." You have to hear Stern growling out those noises to know just what he means. But when he plays, the arghrghrgragh seems to come out like molten gold.