I am always amazed that, after so many years of audiences scrutinizing and admiring symphony orchestra conductors, so little is understood about what the conductor actually does and how he does it. Is he really necessary? Could the orchestra manage just as well without him? What effect does he have on the music? And what goes on between him and the orchestra players?

The best way to provide answers to these questions, recently posed by a friend, was to invite him to a rehearsal and seat him smack in the midst of the orchestra, between the woodwinds and the brass. Not only were his questions answered, but he came away dazzled by the alchemy that exists between the conductor and the players, by the complexity of the relationship, by the tools that must be used to obtain the desired results.

The experience with my friend made me realize that even regular concertgoers may not fully understand just what happens on the podium.

In addition to the basic functions of keeping the orchestra together and preventing one section of the orchestra from overpowering another, the conductor acts like the coach of a team, unifying and inspiring his players to do their best.

An orchestra is composed not only of a hundred artists who play their instruments well, but of individuals, each of whom has a deeply personal idea of how the music should be interpreted. Their diverse approaches to a piece must be unified by their conductor through gesture, eye contact and force of personality--ideally, all without uttering a single word.

Conducting has been aptly described as a "silent art," meaning that at its best, and if the conductor's rapport with the orchestra is great, excellent results can be obtained without a word being spoken. The conductor's physical gestures must, therefore, be communicative enough to transmit to the players the shape and texture of the sounds he is seeking.

Recently at the conducting audition for prospective entrants to the Juilliard School, I was struck by how often the young applicants resorted to speech when just as easily and probably more effectively they could have shown their musical ideas through gesture. In fact, whenever I get together with young conductors who want to discuss their vocation I ask the following question, "Give me, in one grammatically correct sentence, a definition of conducting that you would like to see in a musical encyclopedia." It is surprising how long it takes a group to arrive at what I consider the most obvious and simple definition: Conducting is the transmission of musical impulse through gesture.

The set of gestures used by a conductor is basic and human and is universal in its expression and understanding: A smile of approval is certainly universal, as is a gesture that requests something, that asks for more, or for less. Through a clear beat, the conductor indicates tempo, dynamics, articulation, rhythms and even texture. A communicative conductor can elicit excellent responses from a group with which he has never before worked. An example of this actually occurring was the first performance by Berlioz of his Roman Carnival Overture. Because time had run out at rehearsals, Berlioz never had a chance to rehearse the new work but, as one well-known critic noted, the musical results were so excellent that no one knew of the lack of preparation--so good was Berlioz' conducting technique and his relationship with the players. Every nuance was there.

Individual conductors--like other performing musicians, actors or speakers--can, with the same materials, be either boring or electrifying. No one knows quite why, but this power comes from a combination of energy, sympathy, chemistry and other elusive and undefinable qualities. Why one person is able to mount a podium and, through music, rouse an audience almost to frenzy is not known; musical technique may be taught, but personality and charisma cannot. Nevertheless, a conductor must personify the essence of the music; he must, almost as in mime, convey with his body what is happening.

Orchestras do not need an entire rehearsal to judge a conductor's ability. Indeed, a gut feeling can hit the players the very first moment the conductor steps before them, even before the first downbeat. The very way he walks on stage speaks volumes to an orchestra, even to the point of telling them if he is able, confident, communicative. After this initial moment, it is the same working of chemistry that will determine whether two people become lovers or never see each other again. Often, the relationship between a conductor and orchestra simply does not work; this is not a negative reflection on either party, but is just the result of two strong personalities not being in sympathy.

Under good conditions, the goals of conductor and orchestra are identical: to bring to audiences the best possible performances. In this case, the conductor is captain of a team that cannot possibly lose!