Rumori is a medieval Italian word frequently used for uprising or revolt, and shares the root of English “rumble” and “rumor.” It connotes noise, murmuring, a contagious disruption upsetting civic harmony. This dissertation examines voices of public opinion towards thirteenth-century French conquests in Sicily, and later, Flanders, and the violent uprisings that resulted. Drawing on chronicles (proliferating in the vernaculars as well as Latin), medieval musical scores, and administrative documents, my work aims to reconstruct and overhear a world in which news and public perceptions circulated orally. While the preaching of the mendicant orders has been studied as a form of “mass media,” I suggest that these unofficial communication networks are analogous to what we think of today as “social media” and can tell us a great deal about the cultures and mentalités of the communities in which they circulated.