Notice the room tone
Before a scene becomes frightening, listen for the space it creates. A hum, a distant movement, or a hollow room can establish an atmosphere with very little information. Then notice what disappears. A soundtrack does not have to become louder to make a room feel different. Sometimes a missing familiar sound is the detail that changes everything.
Separate the layers
On a second viewing, try following one layer at a time. Listen to the music, then to the sounds that seem to belong to the room, then to the gaps between them. Ask which layer leads your attention. Do you look toward the door because something moves, or because a sound has already told you to? This is a way of appreciating construction, not a test with a correct answer.
Leave room for contrast
For a horror-night playlist, we like the contrast between sparse passages and denser pieces. Constant intensity can become its own kind of background. A quieter transition gives the next sound an edge again. The same principle guides our visual world: a blank margin, an unlit corner, or a pause can be an active part of the composition.