<P> <I>Musica Naturalis</I> delivers the first systematic account of speculative music theory as a discursive horizon for literary poetics. The title refers to the late medieval French poet Eustache Deschamps, whose 1392 treatise on verse writing, <I>Art de Dictier</I>, famously casts verse as "natural music" in explicit distinction to song, which Deschamps defines as "artificial." Philipp Jeserich begins with Augustine and Boethius and traces the discourse of speculative music theory to the late fifteenth century, giving attention to medieval Latin and vernacular sources. By linking the significance of the speculative branch of medieval musicology to literary theory and literary production, Jeserich opens up a field of study that has been largely neglected. <I>Musica Naturalis</I> reads like a history of speculative music theory and poetics in the Middle Ages. On its basis, Jeserich pleads for the conservatism of Deschamps’s poetics and develops a new perspective on the poetics and poetry of the Grands rhétoriqueurs.</P><P>Given Jeserich's reliance on the intellectual inheritance of late medieval French poetics and poetry, this book will appeal to English-speaking specialists of Old and Middle French, as well as scholars of the French Renaissance. It will also interest English language medievalists of several other disciplines: intellectual historians and specialists of English, as well as scholars of Italian and Iberian literature.</P>