Jean-Benjamin de Laborde's "Abrégé d'un Traité de Composition," Livre III of his encyclopedic "Essai sur la musique ancienne et moderne," represents a new historical sensibility in the field of music theory at the end of the eighteenth century. Since antiquity, music theory has been divided into two main categories, musica speculativa and musica pratica. One, or both, of these approaches to music theory form the foundation of almost every music treatise for over 2,000 years, at least until the eighteenth century. A new historicist methodology appearing during the French Enlightenment treated history as a concept that demonstrated progress; this was accompanied by another emerging viewpoint that regarded historical phenomena as independent entities worthy of study in their original cultural context. Laborde's work incorporates both of these historicist positions, and, in so doing, furnishes a third means to engage in music theory, one that has been termed musica historica in this study. Laborde's "Abrégé d'un Traité de Composition" (1780) incorporates these various aspects of music theory —musica speculativa, musica pratica, and musica historica—within it, with varying degrees of success. Laborde, a composer, writer, fermier-général, and student of Jean-Philippe Rameau, wrote the "Essai" to present all the information on musical subjects that he had discovered. He treats certain topics as speculative, others as practical, and still others as historical, but most of the material blends the three approaches in various ways, allowing Laborde the freedom of a flexible methodology. This dissertation sets Laborde's composition treatise in its historical context, investigating Laborde's life, the culture in which he wrote his treatise, his understanding of ancient music theory, his relationship to contemporary French theorists such as Rameau, Jean le Rond d'Alembert, and Jean-Jacques Rousseau, and how he interprets the history of his theoretical topics. By placing Laborde's "Abrégé d'un Traité de Composition" in its proper historical context, this study illuminates the work of a man who was one of a very few at the end of the eighteenth century to employ the nascent tools of modern historicism to investigate music. This dissertation concludes with a translation of Laborde's composition treatise.
