What Are That in Hindustani Classical Sangeet

The modern thāt system was created by Vishnu Narayan Bhatkhande in the early decades of the twentieth century.Bhatkhande modeled his system after the Carnatic melakarta classification, devised around 1640 A.D. by the musicologist Venkatamakhin. Bhatkhande visited many of the gharanas (schools) of North Indian classical music, conducting a detailed analysis of Indian raga. His research led him to a system of ten thāts, each named after a prominent raga associated with it. Many correspond to one or other of the European church modes. They are listed here according to their pitches; lower-frequency pitches are represented with lowercase letters and higher-frequency pitches with uppercase letters.

• Bilawal (=Ionian mode): S R G m P D N S' - Shankarabharanam
• Khamaj (=Mixolydian mode): S R G m P D n S' -
• Kafi (=Dorian mode): S R g m P D n S'
• Asavari (=Aeolian mode): S R g m P d n S'
• Bhairavi (=Phrygian mode): S r g m P d n S'
• Bhairav: S r G m P d N S' - Mayamalavagowlai
• Kalyan (=Lydian mode): S R G M P D N S'
• Marva: S r G M P D N S'
• Purvi: S r G M P d N S'
• Todi: S r g M P d N S'

One can arbitrarily designate any pitch as Sa (the tonic) and build the series from there. While all thāts contain seven notes, many ragas (of the audav and shadav type) contain fewer than seven and some use more. A raga need not use every swara in a given thāt; the assignment is made according to whatever notes the raga does contain. The relatively small number of thāts reflects Bhatkhande's compromise between accuracy and efficiency: The degree of fit between a raga and its thāt is balanced with the desire to keep the number of basic thāts small.Ambiguities inevitably arise. For example, Raga Hindol, assigned to Kalyan thāt, uses the notes S G M D N, which are also found in Marwa thāt. Raga Jaijaivanti contains both shuddha nishad and komal nishad (and sometimes both versions of gandhar as well), which by definition corresponds to no thāt. Bhatkande resolved such cases "by an ad hoc consideration, appealing to musical performance practice" (see Ramesh Gangolli's article, cited in note 4 above). Each thāt contains a different combination of altered (vikrt) and natural (shuddha) notes. The flattening or sharpening of pitches always occurs with reference to the interval pattern in Bilawal thāt.
In effect only heptatonic diatonic scales are called "thāt." Bhatkhande applied the term "thāt" only to scales that fulfill the following rules:

• A thāt must have seven notes.
• The notes must be in sequence: Sa Re Ga Ma Pa Dha Ni (whether shuddha or vikrt—both versions of a single note are not allowed).
• A thāt, unlike a raga, does not have separate ascending and descending lines.
• A thāt has no emotional quality (which ragas, by definition, do have).

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