The Vijayanagara musicological nonet or the are a group of nine musicological treatises written during the reign of the Vijayanagara empire. These works are counted among the most important and definitive treatises in Carnatic music theory. Each of these works contributed seminally to the growth of the Carnatic music tradition. These nine works are the by the sage Vidyaranya, by Salva Gopa Tippendra, by Kallinatha, Bhandaru Vittaleshwara's commentary on the , Bhandaru Lakshminarayana's , Achyutadevaraya's and the much celebrated by Ramamatya. Historical milieu The reign of Vijayanagara empire was a watershed period in the cultural history of South India, particularly the history of Carnatic music. The period witnessed the prolific contributions of numerous musicians, saints and theoreticians. By virtue of the geo-political influence it exerted, Vijayanagara had become the confluence of many religions, art forms and cultures. Society and culture went through a process of conflict and eclectic assimilation of the traditional and elite values on the one hand and the emerging folk and foreign influences on the other. There was a strong interaction between traditional and elite values on the one hand and folk and foreign influences on the other. Much of this was also the result of a reaction and revolt against emerging sociological and aesthetic trends. Even as this assimilation and nativization of the contending or opposing influences took place, traditional purity and historical continuity continued to be preserved. These cultural trends and objectives were later sustained and fostered in the several feudatory states that continued to thrive beyond the fall of the Vijayanagar empire. Some of the notable states included Anegundi, Penukonda, Tanjore, Mysore Kingdom, Madurai, Ikkeri etc.,. Innovations in theory and practice A wide range of experiments and innovations were carried out in the field of instruments too. The Tamburi introduced during the period soon became the principal drone instrument. Seminal work and innovations also took place in the Vina keyboards with regard to the accordatura, tonal range and instrumental parameters. The replaced the and it's the theoretical possibilities were fully explored through mathematical schemes of tabulation. The innovation of the concept of and organization of the entirety of contemporary melodic material under its umbrella culminated in Venkatamakhin's scheme, one which continues to influence greatly the theory and practice of Carnatic music to this day. New classificatory models emerged for ragas; (upper partials), (alternative svara denomination) and (representative note) scales and intervals were tuned to