Ragas can be classified in lot of different ways, some of which I wrote about earlier. Another way of classification is through “Thaats” (framework) in Hindustani music and “Melas” in Carnatic music. Venkatamakhin’s classification of Ragas and its subsequent development has shaped Carnatic Music. Classification of Ragas was based on the scale used by a Raga and thus, Venkatamakhin classified various scales, called Melas. His system not only classified known Ragas but also introduced several new ones, based on the possibilities that the system of classification he used, threw up. All melas are full scales, having seven notes.
Every Mela has both Sa, the reference and Pa, the secondary reference. Notes, Re, Ga, Dha and Ni are of 3 varieties each. For a mela, one of the three types of each of the four notes needs to be picked up. This gives us 4x3x3=36 possible combinations. Since Ma can be of two types we get a total of 36×2=72 Melas.
Bhatkhande, who came up with a ten Thaat system, classified Hindustani music. These are like the Genera and each Raga classified under it is a species belonging to the Genera. Each of the thaats is named after the most famous Raga using that scale.
The ten thaats used are as follows:
Sa, Re, Ga, ma, Pa, Dha, Ni, Sa’=> C D E F G A B C’ ( all Shudha or natural notes)
Sa,Re,Ga,ma,Pa, Dha,ni,SA’=> C D E F G A Bb C’ (Ni Komal, minor 7th)
Sa, Re, ga, ma, Pa, Dha, ni, SA’=> C D Eb F G A Bb C’ (Ga and Ni Komal, minor 3rd and 7th)
Sa,Re,ga,ma,Pa,dha,ni,Sa’=> C D Eb F G Ab Bb C’ (Ga, Dha,Ni Komal, minor 3rd, 6th and 7th)
Sa,re,Ga,ma,Pa,dha,Ni,Sa’=> C Db E F G Ab B C’ (Re,Dha Komal, minor 2nd, 6th)
Sa,re,ga,ma,Pa,dha,ni,Sa’=> C Db Eb F G Ab Bb C’ (Re,Ga,Dha,Ni komal, minor 2nd,3rd,6th and 7th)
Sa,Re,Ga,Ma,Pa,Dha,Ni,Sa’=> C D E F# G A B C’ (Ma teevra, Augmented 4th)
Sa,re,Ga,Ma,Pa,Dha,Ni,Sa’=> C Db E F# G A B C’ (Re koaml, Ma Teevra, minor 2nd, augmented 4th)
Sa,re,Ga,Ma,Pa,dha,Ni,Sa’=> C Db E F# G Ab B C’ (Re,Dha komal,Ma teevra, minor 2nd, 6th and 7th, augmented 4th)
Sa,re,ga,Ma,Pa,dha,Ni,Sa’=> C Db Eb F# G Ab B C’ (Re,Ga,Dha komal, Ma teevra, minor 2nd,3rd,6th and augmented 4th)
These ten Thaats of Indian classical music correspond with some Western modes:1.Kafi/Dorian 2.Bharavi/Phrygian 3.Yaman/Lydian 4.Khamaj/Mixolydian 5.Asawari/Aeolian 6.Bilawal/Ionian.
The scale above has been written on C scale, but in Indian music the scale of a raga need not start with C, as there is no absolute pitch. The pitch generally depends on the performer. There are several well-known Ragas that do not fit any of these scales, but were subjectively grouped under one of the thaats by Bhatkhande. For this reason, his classification has not been universally accepted by theorists, although it is most widely followed in practice.