Compose around the sound of a scene
Scoring movies is often writing music that needs to fit in a certain frequency range to actually be heard. You need to compete against sound effects and design which in many cases leaves only small possibilities for the music to come through. When you’re for example scoring a dialogue scene in a car, you will most likely have at least a little engine sound on the audio track, together with maybe other traffic noises etc. So in such cases, it’s not the greatest idea to put most of your musical information into the lower register where it collides with the engine sound. Also depending on the sound architecture of the scene, you might want to use a different focus on note lengths. A highly active action scene with lots of different and changing noises might rather call for longer notes in the music to be distinguished from the sound fx (this doesn’t mean that the music needs to be slow as well, just listen to action cues which build up a heavy rhythmic activity but the main focus lies on long notes, for example in the brass) A very constant (and possibly loud) sound atmosphere might be scored with more active elements as they build a better contrast to this atmosphere and therefore might be heard more easily.