Melakarta

There are 10 thaats in Hindustani music, though the commonly accepted melakarta scheme has 72 ragas.

Later, Venkatamakhin, a gifted musicologist in the 17th century, expounded a new mela system known today as mēḷakarta in his work Chaturdandi Prakaasikaa.

[3] He made some bold and controversial claims and defined somewhat arbitrarily 6 svaras from the known 12 semitones, at that time, to arrive at 72 mēḷakarta ragas.

The controversial parts relate to double counting of R2 (and similar svaras) and his exclusive selection of madhyamas for which there is no specific reasoning (also known as asampurna melas as opposed to sampurna ragas).

A hundred years after Venkatamakhin's time the Katapayadi sankhya rule came to be applied to the nomenclature of the mēḷakarta ragas.

The Sanskrit rule of “Sankhyānam vāmatò gatihi” means for arriving to digits, you read from right to left.

For example, Harikambhoji raga starts with syllables Ha and ri, which have numbers 8 and 2 associated with them.

This scheme envisages the lower Sa (Keezh Shadja), upper Sa (Mael Shadja) and Pa (Panchama) as fixed swaras, with the Ma (Madhyama) having two variants and the remaining swaras Ri (Rishabha), Ga (Gandhaara), Dha (Dhaivata) and Ni (Nishaada) as having three variants each.

There are twelve semitones of the octave S, R1, R2=G1, R3=G2, G3, M1, M2, P, D1, D2=N1, D3=N2, N3 (see swaras in Carnatic music for explanation of these notations).

Muthuswami Dikshitar school followed a different set of scales as the 72 Mēḷakarta ragas.