In the basement of Lisbon, an old disused cistern provides the water in the darkness. Under the vaulted space, the stagnant surface of the water is sometimes set in motion by a mechanism which causes a circular wave.
Then the walls and columns of the cistern are streaked with reflections and thousands of layers of light. The sound adds a dimension when it scatters the space with fine drops of water music that release resonances when they hatch.
The undulations gradually disappear in the dark until the emergence of a new wave.