Loudspeakers are everywhere in the built environment. Indeed, music, sound, and listening today are arguably defned by their apparently inevitable mediation by an electronically amplifed loudspeaker. But it wasn’t always so. When and how did that transformation take place? What was its musical and cultural signifcance? Whereas popular and historical accounts tend to emphasize the concentricity of the loudspeaker and rock music, this article roots such developments in an essential but under-researched prehistory, showing how the loudspeaker went from an incredible novelty to a predictable ubiquity between 1915 and 1940. I sketch the loudspeaker’s early history and ofer an assessment of its role in twentieth-century musical and acoustic culture. I suggest that the loudspeaker needs to be understood as a cultural technology in a broader history of sound, and that it played a central role in the formation of modern listening.