Music is not an emotional subtitle
A sad face on screen does not automatically need sad piano. A small low tone just before the scene, or an air that remains unexpectedly bright, can create a deeper tension.
Sound is not there to repeat what is visible. Its task is to decide the emotional direction before the image arrives.
A choice half a beat early
When sound moves one beat first, the audience reacts before it knows why. That tiny lead is the shortest path through surprise, relief, or longing without an explanation.