A raga is one of the melodic modes used in Indian classical music.
A raga uses a series of five or more musical notes upon which a melody is constructed. However, the way the notes are approached and rendered in musical phrases and the mood they convey are more important in defining a raga than the notes themselves. In the Indian musical tradition, rāgas are associated with different times of the day, or with seasons. Indian classical music is always set in a rāga. Non-classical music such as popular Indian film songs and ghazals sometimes use rāgas in their compositions.
Northern and southern differences
The two streams of Indian classical music, Carnatic music and Hindustani music, have independent sets of rāgas. There is some overlap, but more “false friendship” (where rāga names overlap, but rāga form does not). In north India, the rāgas have been primarily categorised into ten thaats or parent scales (by Vishnu Narayan Bhatkhande, 1860-1936); South India uses an older and even more systematic classification scheme called the melakarta classification, with 72 parent (melakarta) rāgas. Overall there is a greater identification of rāga with scale in the south than in the north, where such an identification is impossible. Rāgas in north Indian music system follow the ‘law of consonances’ established by Bharata in his Natyashastra, which does not tolerate deviation even at the shruti level.