There is only one Shinichi Suzuki (the world might not be ready for more than one), but watching the man in action you might swear there were at least four.

Rehearsing 100 student musicians for a concert, he has them so thoroughly trained, so precisely together that he does not have to stay in front of the group keeping time.

He gets them started at the right tempo, then wanders out of the rehearsal hall for a cigarette (Camels, which he smokes in great quantities, using a brown holder), for a quick chat with one of his numerous assistants, a few words with the proud mother of a Suzuki student, to autograph books or programs, or have a photo snapped with a child on his knee.

He is very good with children - patient, gently . . . loving - the word sounds awkward in connection with the bustle and turmoil surrounding a mass rehearsal, but it comes often and naturally to his lips and shows in his every gesture.

The people around Suzuki - there were hundreds of them at the Catholic University School of Music, where he conducted rehearsals on Sunday - talk about him in reverent tones, as though this busy old man were a sort of Buddha.

They may be right. At least, he is the father of a revolutionary idea in music education that implies a whole new orientation to life for children and their parents.

It all began, a long time ago, when Suzuki, then a 18-year-old Japanese violinist, had trouble with the German language.

Suzuki, a member of a family that has been famous for generations as violin-makers, went to Berlin to study under Prof. Karl Klingler. In his struggles with the language, Suzuki could not help noticing that 3-year-old German children spoke it more fluently than he did.

That started him observing the learing abilities of very young children and thinking about these natural abilities could be developed. By now, his observations have helped hundreds of thousands of children to learn to play the violin before they learned ot read.

Some of the Japanese students also learn to read earlier than usual - and in Japanese, which any English-speaker will tell you is impossible to learn. At the same time. they learn to speak English , which any Japanese-speaker will teil you is impossible.

Suzuki is not the first to discover the remarkable learning ability of very young children. Leopold Mozart, a professional musician, discovered it and his son Wolfgang was writing minuets when he was 4 years old. Philosopher John Mills knew it and his son John Stuart Mill was taught Greek when he was 3. Latin when he was 8. Jose Capablanca's father learned it, a bit painfully, when his self-taught son, a future world champion, began beating him at chess when he was 4 years old.

Our language has a word for these people and for others (Blaise Pascal, Yehudi Menuhin, Anna Maria Vera, Paul Morphy and Bobby Fischer) who have shown ununual abilities at an early age. We call them "prodigies," implying that their talent represents a lucky throw of the genetic dice, and we take it for granted that this sort of thing does not happen very often. Suzuki's uniqueness lies in the fact that he can put 100 musical "prodigies" on stage at the same time, all playing a Bach or Vivaldi violin concerto in perfect unison.

He did this at the Kennedy Center Sunday night with a group of 100 Japanese children and another group of 100 Americans. The concert will be repeated during the coming week in Atlanta's Symphony Hall and New York's Carnegie Hall.

Suzuki's basic perception, which dates back to his early experiences in Germany but did not become systematized until the late 1940s, was that children can learn to "speak" music as early and as naturally as they learn to speak their native languages. Later developments by Suzuki and his associates have broadened this basic concept into fields other than music. The results indicate that normal children, at a very early age, are capable of learning at a rate that we usually associate with genius-level intelligence.

It is not necessarily easy - the children should be immersed in a musical atmosphere from their earliest years, and the mother should go through the learning process with the child, for example. And nobody is sure yet whether the total process, as opposed to purely musical skills, can be translated from Japanese into American society.

In terms of pure musical quality, Suzuki-trained children do not set a new standard excpt in terms of their age-group. The string section of the Curtis Institute Orchestra, for example, plays a wider repertoire than the Suzuki group that performed here Sunday night, and plays it with more nuance and finesse. Nevertheless, the sight of 100 choldren (including some who are 3 or 4 years old) playing Bach or Vivaldi and playing it very well, is enough to amaze any music-lover and make any parent wonder what else might be possible.

The most noted critic of Suzuki's approach, which relies heavily on rote learning, with a standard recording that must be played for the child each day, is virtuoso violinist Isaac Stern. He has publicly called the Suzuki approach an "automated procedure" that has become a "very big business to sell violins, cases, bows and instruction books."

With an estimated 100,000 students in this country, Suzuki training had undoubtedly become a "big business," and Suzuki instruction books and records are essential for the training, but Justine Hughes, a Washington mother whose daughter Natalie is studying in the Suzuki style, says none of the students in this area use Suzuki instruments.

"I learned piano by the old method, with a lot of useless theory, scales and other exercises built into the system that were not really music," she said. "I wish I could have learned the way Natalie is learning. When I heard about this method, I knew it would be better, and it is."

Incidentally, Suzuki's concepts and practices also have placed him in the middle of a controversy that has been raging in recent years over the relative importance of heredity and environment in the development of a child's learning abilities. His insistence on a proper environment and on the "genius-level" abilities of an average toddler put him at the opposite pole from some psychologists who insist that large classes of children have limited learning ability because of inherited (some say "racial") deficiencies.

Interviewing Suzuki in English is both a fascinating and a frustrating process. After waxing eloquent, with vivid gestures, in an interview last Sunday about the enormous learning ability of young children, he paused, shrugged and added a little sadly: "My English . . . too late."

He is much more fluent when talking about music than in other areas, and he shows an easy, natural ability to communicate with children no matter what languages are involved. But theoretical discussions of the fairly abstract issues raised by the Suzuki phenomenon tend to be more spectacular than subtle.

With the aid of a translator and gestures as well as key phrases in English ("even Japanese children, living with Japanese music . . . koto, samisen" - accompanied by the gesture of plucking a samisen - "can learn violin easily") he pointed out the tremendous cultural obstacles that are added to other barriers in teaching the violin to a 3-year-old Japanese child.

He said that he is particularly proud of the Early Development Association, which has applied his ideas in a Japanese kindergarten where children as young as 2 years old are taught not only music but spoken English, Kanji (the Japanese written language) and a course called "Thinking" that combines arithmetic with logic and other elements.

Age 3 is already very old for a child to begin formal learning, he said. "Begin at age zero," patting his lean stomach to indicate that a child probably begins learning while still in the womb. He notes with pride that children come out of the kindergarten with average IQs of around 160.

Dr. Masaaki Honda, director of talent education for E.D.A. and a close associate of Suzuki, is considerably more articulate in English. He is reluctant to discuss such subjects as IQ, which is relatively difficult to measure and not fully stabilized in early childhood, and he does not get excited over the spectacular achievements of Suzuki students.

"We are not trying to develop prodigies or an elite group of children," he says. "We are not even trying to develop professional musicians" - a point that may be a relief to those who have wondered what the world could do with a million Menuhins.

"Out goal," Honda continues, "is to develop powers of concentration, memory, above all a devotion of the heart. We are teaching through music a harmonious development of the total personality; our aim is to make each child a good citizen of a better world. They will become doctors, lawyers, businessmen; they will influence their environment and their colleagues, and the skills they learn as very small children will help them to do this."