system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What exactly is a conductor doing?

In classical performances and stuff, besides keeping tempo in check. Is he really needed?
gpt
First, what you don't get to see while watching a performance is all the work a conductor has put into shaping the music. The conductor is much like the director in a movie: they decide how to interpret to music like a director interprets a script, and they select what sounds best. If a piece of music says to slow down, the conductor has to decide *how much* to slow down. They have to decide how certain sections should sound, how to use dynamics effectively, and how the pauses in the music are executed. The conductor also decides, or at least helps decide, who is fit to be in the orchestra, what the proper balance of instruments is, and who should be playing.

Come the time of the performance, the director is in charge of keeping the tempo, yes, regardless of what environment they are playing in, and the ears cannot be totally trusted with keeping tempo. The director also is constantly providing reminders of what they have rehearsed, and is instrumental in keeping everyone together and focused, no pun intended.