[4] The modern thaat system was created by Vishnu Narayan Bhatkhande (1860–1936), an influential musicologist in the field of classical music in the early decades of the twentieth century.
[5][6] Bhatkhande modelled his system after the Carnatic melakarta classification, devised around 1640 by the musicologist Vidwan Venkatamakhin.
Bhatkhande visited many of the gharanas (schools) of classical music, conducting a detailed analysis of ragas.
According to Bhatkhande, each one of the several traditional ragas is based on, or is a variation of, ten basic thaats, or musical scales or frameworks.
The seven basic swaras of the scale are named shadja, rishabh, gandhar, madhyam, pancham, dhaivat and nishad, and are abbreviated to Sa, Ri (Carnatic) or Re (Hindustani), Ga, Ma, Pa, Dha, and Ni and written S, R, G, M, P, D, N. Collectively these notes are known as the sargam (the word is an acronym of the consonants of the first four swaras).
As in Western moveable solfège, Sa refers to the tonic of a piece or scale rather than to any particular pitch.
The flattening or sharpening of pitches always occurs with reference to the interval pattern in Bilawal thaat.
[8] Bhatkhande applied the term thaats only to scales that fulfil the following rules: One can arbitrarily designate any pitch as Sa (the tonic) and build the series from there.
Bhatkande resolved such cases "by an ad hoc consideration, appealing to musical performance practice" (see Ramesh Gangolli's article, cited in note 4 above).
Some ragas have been derived from Carnatic music and hence do not fall in the Hindustani classical thaat system.
Narada's Sangita-Makaranda, written sometime between the 7th and 11th century, gives warnings to musicians against playing ragas at the incorrect time of day.
[12][page needed] Bhatkhande claimed that the correct time to play a raga had a relation to its thaat (and to its vadi).
Also, it is clear in Bhatkhande Sangeet Shastra at various places that the time do not have any importance while reciting a raga.