The design came from observations of children, who were running around a park, hitting the uprights of a railing with a stick. I recalled how I used to do that when I was small. I started to do research: I walked around the city with a notepad and observed how people behave. I created an instrument that uses a typical piece of urban infrastructure: a railing. Each module has eight uprights, or one octave. The frame is made from steel profiles, and the uprights from flattened stainless-steel pipes. The degree of flattening of the pipe indicates the pitch. The electronics inside allow correction of the sound, so that the instrument isn’t loud enough to disturb the surroundings. People like to stop and play it.