In this paper we present a vision system that analyzes the gestures of a noted conductor conducting a real orchestra, a different approach from previous work that allowed users to conduct virtual orchestras with prerecorded scores. We use a low-resolution video sequence of a live performance of the Boston Symphony Orchestra, and we track the conductor's right hand. The tracker output is lined up with the output of an audio beat tracker run on the same sequence. The resulting analysis has numerous implications for the understanding of musical expression and gesture.