This dissertation takes a fine-grained approach to the study of a unique local genre of Spanish-language ballad from southeast Louisiana, the Isleño décima. For over two hundred years, the distal marshlands of lower St. Bernard Parish, Louisiana, have sustained a handful of small communities of farmers, trappers, and fishers, known as the Isleños. Isleños trace their ancestors back to colonists from the Canary Islands who settled here during the Spanish colonial period (1763–1802). Their ballads, décimas, provided the soundtrack for a unique way of life in this marsh frontier. These songs composed a unique local tradition, distinct from the widely distributed eponymous genre of Spanish verse. The central concern of this study lies in the dynamic, mutable, and polysemous musical meanings embodied by the genre over time. It begins with the early history of the genre, from the late nineteenth century to the 1970s, situating the Isleño décima within a broad and diverse circum-Gulf of Mexico cultural milieu, and then narrates a history of the genre as it was collected, celebrated, and ultimately transformed into the icon of Isleño identity in the context of a local ethnic revival. The dissertation then turns to the ethnographic present, a present in which Isleño décimas are no longer sung or transmitted as an active musical tradition, asking how the genre might continue to mean in the absence of a living tradition. Engaging with a diverse range of interdisciplinary theoretical and methodological issues, this dissertation brings a new perspective to this little-known local genre, and brings insights gained from this local case to bear on issues of central concern in ethnomusicology and related fields, including historical and ethnographic methodologies, musical meaning, silence, absence, music sustainability, human ecology, and space.