A raga may be understood as a melodic scale (or mode) created by the permutation and combination of notes, rendered in a specific sequence in both ascent and descent. In other words, it is not only the notes that give the raga its identity but also their sequence. Apart from these two aspects, a ragas identity and beauty are also dependent on characteristic ornamentation and intonation. A raga has an innate capacity to create different moods, independent of lyrics.
STATISTICALLY
i. Over 7.2 million ragas can be formed by permutations and combinations of a minimum of five notes.
ii. Only around 5,000 have been tried and named.
iii. Of these, only about 350-400 are periodically used in concerts.
iv. The ragas used extensively would be between 150 and 200.
The reason for this is not hard to seek. Ragas that have stood the test of time alone are used frequently in concerts. These are easily acceptable to various types of listeners and several of them offer a lot of scope for elaboration.
Broadly classified, ragas can be of two types : Melakarta (parent) ragas and Janya (derived) ragas.
Melakarta Ragas : These are perfect, seven-note scales. The term ‘perfect’ is used to signify that they use one variety of each of the seven notes and follow the same straight sequence in both ascent and descent. In other words, the descent is a mirror image of the ascent. For example, the raga Shankarabhamnam uses the notes S G3 Ml P D2 N3 S (the subscript indicating the type of Ri, Ga, Ma, Da and Ni) in a straight order in ascent and the exact reverse in descent. In Western music, if the tonic note Sa were to be taken as C, the rest of the notes would be D E F G A B and C in both directions. This is the oft-used C-Major scale. In Hindustani music, this raga is called Bilaval.
Were we to substitute M (F) with M2 (F#) in the above, we would end up with an altogether different scale called Kalyani. Shifting the tonic note from Sa (C) to Ma (F) in Shankarabhamnam and rendering the same notes can also produce the raga Kalyani.
There are 72parent scales in Carnatic music, using different combinations of the 16 notes.
Janya Ragas : All other ragas are derived from the melakarta ragas as they borrow the notes from them. Their main characteristics are :
i) These scales need not have all the seven notes. Example : Mohanam, which uses S G3 P D2 S – S D2 P G3 S. (The fourth note Ma and the seventh note Ni are omitted in both directions.) This is a famous pentatonic scale, much used by the Chinese and the Japanese. Since this uses at least some of the notes present in the major scale, it could be said to be a derivative of the major scale. (Actually, this is also considered a derivative of three other parent scales. In such circumstances, the practice is to classify it either on the basis of other ornamental characteristics or, simply, under the first eligible parent scale in the 72-melakarta sequence.)
ii) They need notfollow the chromatic order of ascent and descent. Example : Kedaram, whose notes are S Ivlj G M, P N S – S N3 P Mj G3 S. From the first note Sa, we move to Ma, bypassing Ri and Ga but from Ma, we descend to Ga before proceeding.
iii) They can have different ascending and descending notes. Example : Andolika: S R, M, P N2 S – S N2 D2 M, R, S. Ga and Da are omitted in ascent while Pa and Ga are absent during descent.
iv) They can have more than one value for the same note. Example: Saranga : S R2 G, M, P D2 N3 S – S N3 D, P M, R2 G3 M, R2 S. Both Mas are used in descent.