When you're staring at the ceiling.
If sleep isn't coming, the goal isn't to entertain — it's to give your mind something boring enough that it gives up and lets you go. The albums here are deliberately under-stimulating: slow, low-frequency-heavy ambient, pink-noise-adjacent drones, very soft piano. Set the sleep timer for 30–60 minutes so the music ends if you do drift off. Keep the volume low; the goal is presence, not pressure.