Excellent post from Kottke.org about the role of the music conductor. The thing is, it started as a curious post by the author, and ended up with a response from a professional conductor that made the post epic.
In orchestral conducting, two things are different. First, the musicians don’t need much help keeping time, so the patterns are either heavily modified or abandoned entirely-although you can often see downbeats and things if you look for them. Second, orchestral conductors conduct WAY ahead of the beat the musicians are actually playing. This helps the musicians respond in real time to the conductor’s instructions.