Objective The monumental City Concerts for bells and bell towers devised by the Spanish composer Llorenc Barber have put into practice the sound aspect of more than two hundred cities around the world. Nowadays, they aim at properly precise margins concerning what would be possible to be produced in the city and how it would be received by the citizen. On that basis, the research intends to outline a reliable map of those opportunity domains that could be available for any architect interested in the city sound design. Methodology The three concerts for Madrid (1991, 2000 and 2007) serve as cases of study. Through their bells and towers, scores, images and recordings, the research identifies, classifies and analyses any aspect related with an architectural imagination of urban sound, assessing not only areas, weights, densities, distributions, and durations but also compositional strategies, execution techniques, and sound qualities. It is structured according to the potential sound design dimensions: from the bell space to the territory, going through the bell tower, the building, and the very space of the city. Conclusions The study offers an orderly catalog of sound effects in urban space. Moreover, it shows certain complexity thresholds from which certain sound strategies could no longer be effective and would not reach the spectator. Finally, it points out an elusive scope in which our analysis tools seem to stop working. Aspects such as chance, uncertainty or accident dilute any attempt to anticipate exactly the sonic experience of the city. Originality Focusing on a sole instrument: the bell, on a same urban space: the city of Madrid, and on the language of a single designer: Llorenc Barber, the research may contribute to the progressive definition of a project system concerning how to give sonic shape to the city.