The tenor Gilbert-Louis Duprez is today remembered for his invention of the ‘C from the chest’, first presented to Parisian audiences in 1837. This has retrospectively been mythologised as the origin-point of modern tenor technique, though recent research has thrown the exact nature and significance of Duprez’s achievement into doubt. Nonetheless, one context in which Duprez was understood as revolutionary was in the scientific work of two Lyonnais doctors, Paul Diday and Joseph Pétrequin, whose 1840 essay ‘Mémoire sur une nouvelle espèce de voix chantée’ offers a unique perspective not only on what Duprez sounded like, but also on developments in the understanding of the physiological phenomenon of singing itself. Placing this work in the context of earlier medical writings on the voice, and of the authors’ subsequent debate with the singing teacher Manuel Garcia Jr., suggests that the late 1830s were a period of flux in the history of the understanding of singing, one in which long-held certainties were being questioned. Duprez thus arrived in Paris at a unique moment. The changing conceptual background shaped the understanding of Duprez’s voice even as the tenor was used by the doctors as a ‘living experiment’ to reach conclusions about the function of the voice generally.