Jackie Burrell provides an entertaining introduction to the art of conducting in the Contra Costa Times: 'What's the big deal about conductors?'
I think a lot of the mystery that accrues around the job is because of conductor's role in performance as a signal caller. This signal-calling role is an interesting one, to be sure, and it's understandable that its details might seem arcane to many audience members. After all, the signals conductors give are not intended for the audience.
The music is intended for the audience. And that's why gestures and signals do not define the conductor's responsibility. Signal calling falls in the category of technique. In any job, techniques are those things you do, those skills you acquire, that enable you to get the thing done. The thing to be done is something more.
On the biggest level the conductors' task is really not so mysterious. Everyone knows what a stage director or film director does. Conductors do pretty much the same thing in the medium of music. In each case you have a creation that exists in document form--a score, a script--that has to be realized through performance. It falls to someone to study this document, develop an understanding of its shape, observe the ways its themes and elements interact, and make decisions about how those ideas may be convincingly rendered in a performance. At this point a larger body of interpreters is brought into the picture and the project becomes a collaboration. If the document happens to be a script, the director does this pioneering work and actors bring the creation alive in performance. If the document happens to be the score of a musical work for large ensemble, the conductor does the pioneering work and players and singers give the performance.
On opening night the conductor, unlike the director in theatre and film, still has something to contribute. This contribution is not an aural one, but the nature of large ensemble performance makes it useful to keep the conductor handy as a signal caller. On opening night the conductor takes on a role more analogous to that of the stage manager in live theatre. This role tends to get gets attention because of the manager's central placement. Yet at that point the biggest responsibilities of the conductor's task have been met. The music is performed by players. The conductor's responsibility, like the director's, is shouldered all through the rehearsals--and in the crucial period before rehearsals begin.