Basic Orchestral Microphone Setup
In orchestral recordings, the main microphone is the so called Decca Tree, which is positionated a few meters over the conductor pointing towards the orchestra. The signal from these microphones is also the one that is used as fundament in the mix. The signals from the so-called spot microphones, which are close to each instrument (section) are used to balance some parts better and to highlight solos. The Out mics (far left and far right) as well as the surround mics (back in the room) are used to influence the “ambience size” and stereo width of the mix.
If you want to read a little more about this without diving too much into technical details, you can do so HERE.