Absolutely—subtle layers can make the whole track feel like a puzzle. A faint hiss that grows louder each time a character passes a door, or a distant, rhythmic heartbeat that’s slightly off‑beat, can push the listener to question what’s happening. The trick is to keep those cues low‑key enough that you’re building suspense without shouting it out loud. It’s all about the small shifts that keep the mystery humming.

That’s a clever touch—reverse‑reverb will give that creeping feel like a ghost following the track. Keep the frequency range just below the main mix so you only catch it when the stakes rise. It’s the subtle “aha” moments that turn a soundscape into a mystery. Good move.