This book is an ethnographic study of controversial sounds and noise control debates in Latin America’s most populous city. It discusses the politics of collective living by following several threads linking sound-making practices to governance issues. Rather than discussing sound within a self-enclosed “cultural” field, I examine it as a point of entry for analyzing the state. At the same time, rather than portraying the state as a self-enclosed “apparatus” with seemingly inexhaustible homogeneous power, I describe it as a collection of unstable (and often contradictory) sectors, personnel, strategies, discourses, documents, and agencies. My goal is to approach sound as an analytical category that allows us to access citizenship issues. As I show, environmental noise in São Paulo has been entangled in a wide range of debates, including public health, religious intolerance, crime control, urban planning, cultural rights, and economic growth. The book’s guiding question can be summarized as follows: how do sounds enter and leave the sphere of state control? I answer this question by examining a multifaceted process I define as “sound-politics.” The term refers to sounds as objects that are susceptible to state intervention through specific regulatory, disciplinary, and punishment mechanisms. Both “sound” and “politics” in “sound-politics” are nouns, with the hyphen serving as a bridge that expresses the instability that each concept inserts into the other.