Soundtracks are created to enhance the storytelling on-screen. Necessary in that storytelling is the setting, the characters, their emotions and actions, and a structure of events intended to entice the viewer to commit their attention to the film.
When we write, we see the scene in our mind, imagining the face of our protagonist responding to a situation, or viewing the events from their eyes. In that, the film score is effective at providing those scenes we imagine with the same life and soul they do with film. Just as runners use music to keep them at a pace, writers should utilize music to keep our own pace, as well as to enhance the action and events of our imaginations. Music, as it’s known to, unlocks our ability to think deeper and with greater clarity.
For instance, listening to Elfman’s Sleepy Hollow film score, the music sets your imagination in a particular place, one that is dark, dangerous, and terrifying, and if you listen to it as your craft a horror story, the danger in your story becomes more defined as you can focus through the music. Soon you discover a gruesome detail about your villain that you did not see before. The discovery comes when on the track “The Tree of Death” the entire orchestra screams into higher octaves as a bass drum and cymbal clang and boom underneath and you see the villain so clearly as to be standing in front of him. Had the music not been so effective, or even present, and thus your imagination not supercharged, you may have missed the detail.
The best way I can say it is that music provides the writer with blinders (and I mean the blinders that horses wear) which connects us better to our task at hand and detaches us from everything else (personal life, distractions, bills, etc.).