When the composer Zhou Long was a child, he lived in a traditional courtyard home at the foot of Beijing's bell and drum towers. Twisting the wooden handle of a small rattle-drum as he played with his sister on winter afternoons, he beat a whirring rhythm and wondered what the towers might have sounded like when they still told the time.

Built in 1272 during the Yuan Dynasty (1271-1368), the towers had once housed 25 drums and the largest bell in China. Several times a day, the noise from them announced the passage of the hours. The structures have remained silent since 1924, when the last emperor of the Qing Dynasty (1644-1911) was forced to leave the Forbidden City.

"During my childhood, there was no sound," Zhou says. "The towers were silent. I would walk by and feel so much curiosity about these towers. I thought about that huge bell just sitting there on the ground, and I would let myself imagine."