A single note at 5am

Last night I dreamed I was walking through my city at 5am. The streets were wet, and I could smell the river. I passed a jazz club with the door ajar, and there was a saxophone playing a single note, over and over. I stood there for what felt like hours. When I woke up, I realized I've been holding my breath during silent moments in the lab, too — they're not empty, they're the same thing.