I notice Leonard Bernstein often conducts very expressively while leaving the time signature out of his gestures. I notice this especially when he conducts pieces that were written by Mozart. If he leaves the time signature and even the tempo(conducting at a slower tempo than the piece) out, how does the orchestra know where to accentuate the notes and how to synchronize each others instruments so that it sounds good?
Here is an example of what I am talking about. It is symphony no. 40 by Mozart