North Indian classical music is being developed for more than 4000 years into its contemporary styles of instrumental and vocal performance. The music of India, both North and South, is based on the ancient principles of Raga and Tala, or melody and rhythm, although in each system the rags and talas are somewhat different. Raga, or melody, has no exact definition in western musical terminology.

Ragas

Ragas are defined by the notes used in the scale, but some ragas use the same notes yet are recognized as different, so scale alone is not the only feature that separates them. The element of Rasa, or the feelings expressed by a raga, is the distinguishing characteristic which makes a raga more than just a scale or series of notes.

In the 20th century, some of the important factors which define ragas are Thaat or mode, Jati or scale permutation, Prahar or time of day, and Gharana or the musical tradition in which any musician may have been trained.

Many musicians use a system of 10 Thats, or parent modes, to group North Indian ragas. This system is not perfect, because there are numerous ragas which do not quite fit into the scales. However, it is a generally useful heuristic device. They are named for prominent ragas which use the notes of the mode,but they are not identical to the ragas for which they are named; raga Marwa for instance has no Pa. The following table lists all the 10 thaats according to their characters. The links to individual thaat will take you to the list of raags belonging to that thaat.

Individual raga in the above links is displayed as follows

JATI
AROHA
ABOROHA
VADI
SAMVADI
PAKAD
TIME
RAS

Jati

Jati is a method of classifying ragas according to how many notes are used. According to this theory, a raga may have 5, 6, or 7 notes in ascent and 5,6, or 7 notes in descent. This gives 9 possible permutations as follows:

5 notes up 5 notes down called Aurav - Aurav (pentatonic scale)
5 notes up 6 notes down called Aurav - Sharav
5 notes up 7 notes down called Aurav - Sampurn
6 notes up 5 notes down called Sharav - Aurav
6 notes up 6 notes down called Sharav - Sharav (hexatonic scale)
6 notes up 7 notes down called Sharav - Sampurn
7 notes up 5 notes down called Sampurn - Aurav
7 notes up 6 notes down called Sampurn - Sharav
7 notes up 7 notes down called Sampurn - Sampurn (heptatonic scale)

The time of day a raga belongs to is expressed in Prahara, and refers to the any of the eight watches of the day and night. The daytime has four praharas as well as the night. The prahars of the day has been expressed as D-1, D-2, D-3, D-4 and the prahars of the night has been expressed as N-1, N-2, N-3, N-4
The time of day, such as evening or midnight, is an important emotional component of a classical performance. One of the differences between North and South Indian music in this century is the observance of time of day in North India, while this concept has been abandoned in the South.

New Raags