system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the point of a conductor in an orchestra when everyone knows what they are playing?
gpt
Everyone knows their parts and can play it nice on their own but once you have to coordinate a complex piece of music with lots of other musicians it can be very hard. First of all sound takes some time to travel from one side of the stage to the other. So if you were to base your tempo on someone across the room you will be off and it will sound horrible. So you need to use visuals to find the tempo as light travels much faster. This is why the conductor swings his arms in beat with the music. But there is also a lot of other things that is different each time you play a piece. The performers are in different states of mind, the instruments might be affected by temperature and humidity, the sound changes depending on the room, the audience act differently, etc. So the conductor is "playing" on the performers as if they were a big instrument. If one section of the band is too loud he can tell them to bring it down, if someone gets out of beat he can tell them to they are ahead or behind, some pieces have sections that is deliberately changing beat or does not have a beat and it is up to the conductor to find the right timing, etc. Basically if you have a large group of musicians you need someone to coordinate them to make great music.