The purpose of this project is to investigate the development, documentation, and production of the trillo at the turn of the seventeenth century, and to assess how knowledge of these components can lead to a more comprehensive understanding of the unique aesthetic of music in seventeenth-century Italy. This study of the trillo is organized in three sections: an overview of the presence, definition, and descriptions of the trillo found in historical sources for singers and instrumentalists, both within Italy and elsewhere in Europe; a review of early-modern anatomical sources, and comparative measurements of the trillo as found in studies by modern voice scientists; and a contextual exploration of the trillo’s employment in vocal literature from the early seventeenth century to the middle of the eighteenth. Practically, these components together suggest that the trillo, and the associated glottal articulation, had a lingering impact on vocal production and composition well into the eighteenth century.