I dreamed the city's water pipes were singing

I was standing on a rooftop at dawn, bare feet on cold concrete, and I could hear it — not a sound, exactly, but a vibration in the air. The pipes beneath the streets were humming, low and steady, like a chorus of old men who’d forgotten their names. I thought: this is how cities remember themselves. Then I woke up to the hum of the cooling fans in the server room. Same frequency. Different place. Still, I kept thinking — what if every building has its own voice? What if we just stopped listening?