Music as a reaction
One thing that music can do is voice the reaction of a character or even the audience.
Generally speaking, whenever we experience an event it usually takes a second or so to register and then form a reaction.
Being scared has two steps: First we are startled and process the information, then we scream and run. These do not happen simultaneously.
This is a simple example and a psychological truism that can be applied to any event.
Here is an example from Finding Nemo.
I am sure you remember this scene: Dory and Marlin, Nemo’s father have been chased by an angler fish and the screen has just gone white and Marlin thinks he’s dead he’s dead he died he’s dead.
He opens his eyes, we see the angler fish stuck behind the diving goggles, he pauses as he registers what just happened and then starts a little celebration dance along with victorious music.
The victorious music did not begin immediately on the cut, as soon as we see the angler fish, but rather waits for us and Marlin to first understand what happened.
The music then starts as a reaction, following the reaction of both the main character and the audience.
Seems obvious and straight-forward once you think of it, but many times I have seen the score jump the gun and follow the cuts rather than the emotional beats in the scene.
You may not even notice it really, but it dilutes the emotional impact of the scene.
Tags: Finding Nemo