Mix Delivery in Stems
When delivering the music to the film mix, often a separation into so-called stems is requested, meaning that you don’t deliver a complete mix but several tracks with different instruments like one for woodwinds, one for brass etc. This gives more control in the mix to adjust volumes to the rest of the audio in the movie and when for example an oboe is too present against the dialogue, you can take it down a bit without needing to take down the rest of the orchestra.
However, this is quite dangerous when you’re not present on the final mix as some mixing engineers might alter the balance of some of your cues to the extreme. Also, when you have a recording of a live orchestra, delivering in stems is less useful as you might have every instrument on every microphone anyway. However, in such cases it helps to deliver the orchestra and any prerecorded/synth elements separately. The most important thing is to make sure that you are present on the mix and can intervene in case some mix will become too different to what you had in mind.