A thaat is a musical mode in Hindustani music which always has seven notes (excluding the repeated tonic) and is considered the basis for the system of organizing and classifying ragas in North Indian classical music. The notion of thaat, and the ten basic categories, were created by Pt. Vishnu Narayan Bhatkhande in the early decades of the twentieth century^{[1] [2]} . In music, a mode is an ordered series of musical intervals, which, along with the key or tonic, define the pitches. ... Hindustani (हिन्‍दुस्‍थानी) classical music is an Indian classical music tradition originating in the North of the Indian subcontinent circa the 13th and 14th centuries CE. Developing a strong and diverse tradition over several centuries, it has contemporary... Raga (राग) (rāg /राग (Hindi), raga (Anglicised from rāgaḥ/रागः (Sanskrit)) or rāgam /ராகம் (Tamil)) are the very detailed melodic modes used in Indian classical music. ... Vishnu Narayan Bhatkhande Pandit Vishnu Narayan Bhatkhande (August 10, 1860 – September 19, 1936) was an Indian classical musician widely acclaimed to have brought in a renaissance in Indian music. ...

A thaat is a specific set of notes or swara. The idea for Thaat or mode originated in the Carnatic music tradition, where it was described as mela around 1640 A.D. by the musicologist Venkatamakhi. Bhatkhande visited many of the gharanas or traditions of Indian Classical music, and conducted a detailed analysis of the Indian Raga system, to come up with this set of ten thaats - this reflected a tradeoff between the degree of fit between a raga and its thaat, and the keeping the number of basic thaats small^[3]. The notes, or swaras, of Indian music are Shadjam, Rishabham, Gandharam, Madhyamam, Panchamam, Dhaivatam and Nishadam. ... Carnatic music, also known as is one of the two styles of Indian classical music, the other being Hindustani music. ... A musicologist is someone who studies musicology. ... For the 1961 Hindi film, see Gharana. ...

Each thaat contains a different combination of altered (vikrt) and natural (shuddha) notes. The flatting or sharping of pitches always occurs with reference to the interval pattern in Bilawal thaat. It is important to note that, as in the Western church modes, each thaat is a series of intervals, not a series of notes. That is, one can arbitrarily designate any pitch as Sa (the tonic) and build the series from there. In music, a mode is an ordered series of musical intervals, which, along with the key or tonic, define the pitches. ... The tonic is the first note of a musical scale, and in the tonal method of music composition it is extremely important. ...

There are ten generally accepted thaats:

1. Bilawal (=Ionian mode): S R G m P D N S'
2. Khamaj (=Mixolydian mode): S R G m P D n S'
3. Kafi (=Dorian mode): S R g m P D n S'
4. Asavari (=Aeolian mode): S R g m P d n S'
5. Bhairavi (=Phrygian mode): S r g m P d n S'
6. Bhairav: S r G m P d N S'
7. Kalyan (=Lydian mode): S R G M P D N S'
8. Marwa: S r G M P D N S'
9. Purvi: S r G M P d N S'
10. Todi: S r g M P d N S'

Bilawal is the basic thaat (musical mode) in Hindustani classical music. ... The Ionian mode is a musical mode or diatonic scale. ... Khamaj is one of the ten Thaats (parent scales) of Hindustani music. ... The Mixolydian mode is a musical mode or diatonic scale. ... Due to historical confusion, Dorian mode can refer to two very different musical modes or diatonic scales. ... Asavari or Asawari is a Hindustani classical raga. ... The Aeolian mode comprises a musical mode or diatonic scale. ... Due to historical confusion, Phrygian mode can refer to two very different musical modes or diatonic scales. ... Due to historical confusion, Lydian mode can refer to two very different musical modes or diatonic scales. ...

Reference

1. ^ Hindustani Sangeetha Padhathi (4 volumes, Marathi) (1909-1932). Vishnu Narayan Bhatkhande. Sangeet Karyalaya (1990 reprint). This is the book in which Bhatkhande, after thorough analysis, makes the case for the ten Thaats. It has been widely translated.
2. ^ A Short Historical Survey of the Music of Upper India (1974). Vishnu Narayan Bhatkhande. Indian Musicological Society. 
3. ^ Ramesh Gangolli (1992-12-23). Chatura Pandit : V.N.Bhatkhande. Retrieved on 2007-04-11.