The legend of the origin of Indian music dates back to Vedic times. It is said the the Universe itself began with the cosmic sound, Om. This sound is equated with the tonic or base note, Sa. Sa and Pa (a fifth interval) form the base notes of Indian classical music.
With Sa and Pa emanating from the Universe and sustaining it, the other five With Sa and Pa emanating from the Universe and sustaining it, the other five the mouth of each of his faces emanated the five other swaras: Ri, Ga, Ma, Da, Ni. Thus the first raga, karaharapriya (in Carnatic music) or kapi (in Hindustani music), was born.
Even the chanting of the Vedas involved the swaras: Ni, Sa, Ri, and occasionally Pa.
The story of Ravana (the great king who later stole Sita in the Ramayana) also involves music. Ravana did great tapas, with fire, on one leg, and of such great intensity. It is said that Ravana tore his chest open and use his gut-strings as an instrument (like the veena) to play beautiful music upon. His auterities were so severe that soft-hearted Lord Brahma came to grant him any boon except that of immortality. Ravana asked taht he might not be killed by anyone or anything (but out of his ego or carelessness omitted man from his list). Thus is it said that Lord Vishnu came in the form of a man, Rama, to destroy Ravana.
Humans are supposed to have received music only from the gods coming down to Earth with books. Saint Thyagaraja of Carnatic music is said to have received music through books given to him from the gods by Sage Narada.