This project argues that changes to operatic vocal writing in the late nineteenth century prompted Austro-German operagoers to radically expand their understandings of vocal sound in the years around 1900. As post-Wagnerian composers granted greater melodic expression to the orchestra, and increasingly exploited non-melodic vocal effects such as groans and cries, fierce debates were launched about what and how opera’s voices ought to communicate. I track the fallout from these developments, drawing on an archive of journalistic music criticism, vocal treatises, and singer memoirs, as well as under-examined sources such as letters to newspapers, satire, poetry, and cartoons. Listeners looked far beyond the theater to interpret the shifting vocal terrain, enlisting operatic voices in such urgent fin-de-siècle projects as the fortification of human agency amidst industrial creep and the development of a middle-class resistance to elite aesthetics. By showing how they used operatic voices to comprehend and to construct the world around them—especially through emerging, abstract notions of “voice”—I not only provide new examples of the ways in which musical experiences can condition political thought, but reveal several new dimensions to the role of opera in sociopolitical change.