A friend of mine linked to an NPR story called “What Happened to Leonard Bernstein’s Hands?”, which includes this wonderful video (watch what he does after the first 8 or 9 seconds):
As my teacher, the late Frederik Prausnitz, used to say, “You just have to figure out where you need to beat. It is a myth that orchestras need every beat of every bar. Some bars they don’t need it altogether.”
Giving a clear beat is in some sense both the most fundamental and the least important thing that a conductor can do. This Bernstein video is kind of an edge case, but it’s very illustrative nonetheless. Bernstein was a great conductor, and the Vienna Philharmonic is a great orchestra, and they worked together often and had a close relationship. Haydn’s music is not technically challenging for this orchestra; they could probably play it quite well with their eyes closed. And in this particular case, what the video shows is an encore of a movement they had just finished performing, with Bernstein conducting normally.
So does all this mean that Bernstein is doing nothing and just letting the orchestra have at it? Not at all. A conductor’s face can be as important as his hands in communicating with an orchestra (if not more so), and Bernstein had a very expressive face. What he is showing, very clearly, is the desired character of the music, along with an indication of how different parts of the orchestra take the lead at different times.
Most importantly, his face telegraphs changes in the music right before they take place, just like a good preparatory beat with the baton.