A Thaat (that) is a "Parent scale" in North Indian or Hindustani music. It is the Hindustani equivalent of the term Melakartha raga of Carnatic Music.

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In Indian classical music, musical notes are called swaras. 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). Sargam is the Indian equivalent to solfège, a technique for the teaching of sight-singing. The tone Sa is not associated with any particular pitch. As in Western moveable solfège, Sa refers to the tonic of a piece or scale rather than to any particular pitch.

In Bhatkhande's system, the basic mode of reference is that which is equivalent to the Western Ionian mode or major scale (called Bilawal thaat in Hindustani music, Dheerasankarabharanam in Carnatic). The flattening or sharpening of pitches always occurs with reference to the interval pattern in Bilawal thaat. Each thaat contains a different combination of altered (vikrt) and natural (shuddha) notes with respect to the Bilawal thaat. In any seven-tone scale (starting with S, R, G, D, and N can be natural (shuddha, lit. "pure") or flat (komal, lit. "soft") but never sharp, whereas the M can be natural or sharp (tivra, lit. "fast") but never flat, making twelve notes as in the Western chromatic scale. The sharp or flat tones are called vikrt swara (vikrt, lit. "altered"). Selecting seven tones in ascending order, where S and P are always natural whereas five other tones (R, G, M, D, N) can assume only one of its two possible forms, results in 25 = 32 possible modes which are known as thaats. Out of these thirty-two possibilities, Bhatkhande chose to highlight only ten thaats prominent in his days.

In effect only heptatonic scales are called thaats.[8] Bhatkhande applied the term thaats only to scales that fulfil the following rules:

• A thaat must have seven tones out of the twelve tones [seven natural, four flat (Re, Ga, Dha, Ni), one sharp (Ma)]

• The tones must be in ascending sequence: Sa Re Ga Ma Pa Dha Ni

• A thaat cannot contain both the natural and altered versions of a note

• A thaat, unlike a raga, does not have separate ascending and descending lines

• A thaat has no emotional quality (which ragas, by definition, do have)

• Thaats are not sung but the ragas produced from the thaats are sung

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The 10 Common Thats of North Indian Classical Music (Western Mode)

Bilawal (Ionian)

Kalyan (Lydian)

Bhairav

Bhairavi (Phrygian)

Khammaj (Mixolydian)

Kafi (Dorian)

Asawari (Aeolian)

Marwa

Purvi

Todi