6th to 8th century CE, on Indian classical music, attributed to Mataṅga Muni.
It is the first text to speak directly of the raga and to distinguish marga ("classical") from desi ("folk") music.
It also introduced sargam solfège (or solfa), the singing of the first syllable of the names of the musical notes, as an aid to learning and performance.
(The full names of the notes existed previously, for example as found in Natya Shastra.)
[1] The text of Brihaddeshi was edited by Prem Lata Sharma for the Indira Kalakendra series of original texts on the Indian arts and was published as a book "Matanga and His Work Brihaddesi" in 1992.