Mix Automations in Orchestral Music
Mix Automations are pretty common in music productions. It basically means that you program parameters of the mix (like fader levels, pan, reverbs etc.) to change automatically during the course of the track, e.g. raising the levels of one instruments during the chorus and moving it back during verses. This can help to create a specific sound or dramaturgic idea in the mix.
With orchestral music, things are a little different. The ideal should be to do as little volume automation as possible with such music. In recordings of classical music automation should be avoided completely. Reasons for that are that the way orchestras are recorded you will usually not have isolated signals that you can move independently. It will generally work to raise signals in a narrow range on spot mics to give a little more definition or volume to the player or section and it will also work to automate volume on all mics simultaneously to shape big dynamic arks like tutti crescendos but all of this should stay within reasonable limits.
Automations on other paramenters are a little more forgiving except panning automations (which is only reasonable to pull soloists who sit off center closer into the center). What actually works quite nicely is to raise the level of reverb (or even add specific reverb) on the spot mic in solo lines to give that solo a little bit more shine and “drama”. Also, EQ automations when needed (e.g. to control a frequency buildup only in problematic passages) are usually not as problematic.
Of course, always use your ear to determine whether all these automations are still believeable. As stated earlier, a good recording of good musicians playing a well orchestrated and balanced piece of music should not need much of that so rather than tackling any problems on the mix level, try to catch them already in the steps before that.