In this aricle, I argue that Descartes can be seen as a occupying a distinct middle ground between ancient music theory, which was being revived in the Renaissance, and eighteenth-century aestheticians. Descartes’ approach to music had its roots in humanist thought but, even from the start, it wasn’t simply another humanist theory of music. The views Descartes begins to develop in his early years, in the Compendium musicae (1618), is continuous with the views he articulates near the end of his life in the Passions of the Soul (1649). And the position on the effects of music is an interesting and important one, bridging humanist thought with the new philosophy. Unlike the humanists, Descartes will be unwilling to identify particular musical proportions as intrinsically connected with pleasure or other affects, but he will nevertheless develop an objective account of aesthetic value.