Paul Bouissac: The Semiotics of Performances. 
Bloomsbury Publishing, New York 2025, 65 

„Another significant example shows that a performance itself can be immersed into the everyday life of the audience ... Walter Siegfried sung arias that were acquiring new meanings because of their particular urban settings and the unusual delivery of the performance in the form of an exploratory walk in the city. Of course, these events required careful planning and the proper authorizations of the city officials. However, those who were present at the publicly announced locations and those who just happened to be there or to pass by experienced the performance as a spontaneous, innovative, and free event totally immersed in the ordinary life of the city.“