In eighteenth-century France, music was everywhere. Musical criticism and scores filled journals and newspapers, new concert houses and music shops spread across Paris, most authors addressed music in their writings, and pre-revolutionary speeches provided musical metaphors to conjure social and political ideals. Why did music arouse such a widespread interest in this significant period of French history? This dissertation engages with this question using a large body of sources, including print, patents, paintings and engravings, and surviving instruments. Interweaving manifold cultural practices and social actors, it enquires how people defined and experienced what music was, what it did, and who was entitled to practice and appreciate it in eighteenth-century France. I argue that music was conceived as an Enlightened and collective project throughout the century, especially through the changing appropriations of notions of musical harmony. The narrative of this dissertation moves from the exploration of musical harmony as an Enlightened science in the first half of the century, to the appropriation of Rameau’s system of harmony as the summit of French genius and national character in mid-century. It also moves from the negotiation and dissemination of ideas of music through corporeal and material practices, to the uses of harmony as a model for envisaging an ideal socio-political order during the French Revolution. Accordingly, this dissertation features a wide array of social actors who navigated and claimed taste and expertise in this changing musical culture, including musical amateurs, savants, performers, teachers, inventors, and listeners.