Brihaddeshi is a 6th-8th CCE Indian text on music by Matanga Muni. It is the first text that speaks directly of the raga and distinguishes the classical (marga) and the folk (desi). It also introduced sargam notation. In Matanga's discussion of musical scales and micro-tonal intervals he clarifies Bharata Muni's Natya Shastra on which the author based his work. It clarifies many issues related to shruti that were presented tersely by Bharata.
By the time of Matanga there was no need to combine music with Nritya (dance). These ideas have been discussed in detail by modern thinkers like Jaidev Singh, Acharya Brahaspati and Dr. Lalmani Misra. The text of Brihaddeshi was edited by the musicologist Prem Lata Sharma for the Indira Kalakendra series of original texts on the Indian arts.
Website omenad has several articles dealing with ancient and modern theories on Indian Classical music.