Watch this short excerpt of the famous composer and conductor Leonard Bernstein working with some triangle (percussion) players. It’s a good example of how a conductor tries to get the instrumentalists to play JUST the way he wants!
Now watch this video of several famous conductors during rehearsals. Do you see how they try to get the musicians to play the music they way they see it in their head, almost like a painter tries to get things onto a canvas that they see in their head?