Scholarship on urban culture and the senses has traditionally focused on the study of literature and the visual arts. Recent decades have seen a surge of interest in the effects of sound on the urban space and its population. These studies analyze how sound generates identities that are often fragmentary and mutually conflicting. They have also explored the rise of campaigns against the negative effects of noise on the nerves and health of the population. However, little research has been carried out on the impact of sound and music in areas of broader social and political concern, such as social aid, hygiene, and social control. Based on a detailed study of Madrid from the 1850s to the 1930s, this book argues that sound and music have played a key role in structuring the transition to modernity by helping to negotiate social attitudes and legal responses to problems such as poverty, insalubrity, and crime. Attempts to control the social groups that own unwanted musical practices such as organ-grinding and flamenco performances in taverns raised awareness about public hygiene, alcoholism, and crime and triggered legal reform in these areas. In addition to marginalizing and persecuting these musical practices, the authorities and the media used workhouse bands as instruments of social control to spread “aural hygiene” across the city and wipe out unwanted musical practices.