This dissertation contains the first complete Latin-English translation of one of the most controversial music theory treatises of the fifteenth-century: the Musica Practica (Bologna, 1942) of Bartolomeo Ramos de Pareia. its title as well as its content illustrate the Renaissance transformation from the abstract mathematical approach of "musica speculativa" to that of an emphasis upon the everyday demands of the practicing musician. Although Ramos provides traditional explanations of the modes, counterpoint, "musica ficta," and white mensural notation, his innovations in temperament, solmization, mutation, and the gamut set this treatise apart from other ffifteenth-century music treatises. Ramos's rejection of traditional Pythagorean-Boethian-Guidonian explanations, coupled with his strong polemic criticisms of the auctoritas, resulted in a treatise that remained at the center of heated debate well into the sixteenth century.