In Hindustani (North Indian) classical music system, a thaat represents a Parent Scale that uses at least 7 swars/notes(out of the 12 swars) to make a Raaga or Raag. Out of these seven notes–sa re ga ma pa dha ni–Sa and Pa remains constant without variations but other notes: re ga ma dha and ni each have two variants (natural vs. flat, or natural vs. sharp), so there is a possibility of getting 32 different thaats, but 10 thaats are commonly used in Hindustani music.

Pandit Vishnunarayan Bhatkhande:

The modern thaat system was created by Vishnu narayan Bhatkhande(1860–1936). He modelled his system after the Melakartha system of carnatic music classification.

A Thaat always has 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

Pandit Bhatkhande outlined 10 Thaats as follows:

1. Kalyaan Thaat – This Thaat has a group of evening ragas. As this Thaat is considered as a blessing-seeking and soothing. it is sung at the beginning of a concert in the evening. Like Bhairav, this Thaat too is vast and so has many variations like Shuddha Kalyan, Shyam Kalyan, Yaman Kalyan, Anandi Kalyan, Khem Kalyan (Haunsdhwani + Yaman), Savani Kalyan etc.
2. Bilaawal Thaat It’s the most fundamental of all the ten Thaats and is related to the morning.
3. Khamaaj Thaat – It is obtained by replacing the Shuddha Nishad of Bilawal by Komal Nishad. Its nature is romantic (Shringar Ras).
4. Bhairav Thaat – Bhairav Thaat uses Komal Rishabh and Komal Dhaivat. It has manly and austere feelings. Itf is exceptionally huge and so constitutes a large number of note combinations like Ahir Bhairav, Alam Bhairav, Anand Bhairav, Bairagi Bhairav, Beehad Bhairav, Bhavmat Bhairav, Devata Bhairav, Gauri Bhairav, Nat Bhairav, Shivmat Bhairav etc. It is typically sung in a devotional mood in the early morning.
5. Poorvi Thaat – This is the mixture of komal Dhaivat to Marwa Thaat. It is intensely sober and is sung at the sunset.
6. Maarva Thaat – It’s a combination of komal Rishabh and Kalyan Thaat. This Thaat coveys the mood of the sunset and so has a feeling of nervousness.
7. Kaafi Thaat – Kafi Thaat uses the Komal Gandhar and Komal Nishad. It’s a late evening raga and is associated with the spring.
8. Aasaavari Thaat – Asavari Thaat is a blend of Komal Dhaivat and Kafi Thaat. It has the nature of renunciation and sacrifice as well as suffering. It is apt for late morning.
9. Bhairavi Thaat – Bhairavi uses all the komal swars, Rishabh, Gandhar, Dhaivat, Nishad. Bhairavi Raga is named after the cosmic feminine power (i.e. Shakti or Maa Durga). It conveys the feeling of devotion and compassion. It is actually sung in the early morning, yet customarily its singing ends the program.
10. Todi Thaat – This is regarded as the king of all Thaats, as symbolizes pleased worship with a placid, warm outlook and is sung in the late morning.

The specifications of each of the above thaats and popular Raagas in each Thaat are given below:

1. Kalyaan Thaat : S R G Ḿ P D N (Teevra Madhyam Ḿ)

Raagas: Kalyaan/ Shuddha Kalyaan, Shyam Kalyan, Bhupaali, Chaandni Kedaar, Chhayaanat, Gaud Saarang, Hameer, Hindol, Kaamod, Kedaar, Nand, Yaman/ Aiman, Yaman Kalyaan

2. Bilaawal Thaat : S R G M P D N (All Shuddha Swars)

Raagas: Bilaawal/ Alahiya Bilaawal, Bihaag, Nat Bihaag, Bihaagada, Deshkaar/ Desikaar, Durga, Hamsadhwani, Hemkalyaan, Kaushik Dhwani, Shankara

3. Khamaaj Thaat : S R G M P D n (Only Nishaad n is komal)

Raagas: Khamaaj, Desh, Gara, Gaud Malhaar, Gaawati, Gorakh Kalyaan, Jayjayvanti, Jhinjhoti, Jog, Kalaavati, Rageshri, Saraswati, Sorat, Tilak Kaamod, Tilang

4. Bhairav Thaat : S r G M P d N (Rishabh r and Dhaivat d are komal)

Raagas: Bhairav, Ahir-Bhairav, Nat-Bhairav, Gauri, Gunkali, Jogia, Kaalingadaa, Ramkali, Vibhaas

5. Poorvi Thaat : S r G Ḿ P d N (Rishabh r, Dhaivat d, both are komal; and Madhyam Ḿ is Teevra)

Raagas: Poorvi, Basant, Lakshmi Kalyaan, Lalit, Paraj, Puriyaa Dhanashri, Shree

6. Maarva Thaat : S r G Ḿ P D N (Rishabh r is komal, Madhyam Ḿ is Teevra)

Raagas: Maarwa, Bhankar, Bhatiyaar, Lalit, Puriyaa, Puriyaa Kalyaan, Sohini, Vibhaas

7. Kaafi Thaat : S R g M P D n (Gaandhaar g, Nishaad n, both are komal)

Raagas: Kaafi, Abhogi, Bageshri, Bahaar, Barwaa, Bhimpalaasi, Brindaavani Saarang, Chandrakauns, Dhaani, Jog, Megh, Ramdaasi Malhaar, Surdaasi Malhaar, Mian Malhar, Nayaki Kaanhadaa, Patdeep/ Patdeepki/ Pradipki, Piloo, Shahana, Shuddha Saarang

8. Aasaavari Thaat : S R g M P d n (Gaandhaar g, Dhaivat d, and Nishaad n, all three are komal)

Raagas: Aasaavari, Adaanaa, Darbaari Kaanhadaa, Kaunsi Kaanhadaa, Desi, Dev Gandhaar, Jaunpuri

9. Bhairavi Thaat : S r g M P d n (Rishabh r, Gaandhaar g, Dhaivat d, and Nishaad n, all four are komal)

Raagas: Bhairavi, Bhupal Todi, Bilaskhaani Todi, Komal Rishabh Aasaavari, Maalkauns

10. Todi Thaat : S r g Ḿ P d N (Rishabh r, Gaandhaar g, and Dhaivat d, all three are komal; and Madhyam Ḿ is Teevra)

Raagas: Todi, Gurjari Todi, Lilaavati, Madhuvanti, Multaani

Comparison of Hindustani Thaats with Carnatic Raagas

No	Thaat	Raaga	Notes(Sargam)	Western	Mela	Carnatic
1	Bilaval	Bilaval	S R G M P D N Ś	Ionian	29th	Dheerashankarabharanam
2	Kafi	Kafi	S R g M P D n Ś	Dorian	22nd	Kharaharapriya
3	Bhairavi	Bhairavi	S r g M P d n Ś	Phrygian	8th	Hanumatodi
4	Kalyan	Yaman	S R G m P D N Ś	Lydian	65th	(Mecha) Kalyani
5	Khamaj	Khamaj	S R G M P D n Ś	Mixolydian	28th	Harikambhoji
6	Asavari	Asavari	S R g M P d n Ś	Aeolian	20th	Natabhairavi
7	Bhairav	Bhairav	S r G M P d N Ś	Double Harmonic	15th	Mayamalavagowla
8	Marva	Marva	S r G m P D N Ś	–	53rd	Gamanashrama
9	Poorvi	Poorvi	S r G m P d N Ś	–	51st	Kamavardhani
10	Todi	Miyan ki Todi	S r g m P d N Ś	–	45th	Shubhapantuvarali