What are Sruti or Shruti in Hindustani Classical Music: History Origin and Facts

sruti notes in indian classical music

What are Shruti/Sruti? 

To understand what Sruti is, first you need to understand how the octaves are defined. When you sing the Saragam (Sa Re Ga Ma Pa Dha Ni SA), the first Sa and the second SA always have a relation in their frequencies, that is, the frequency of SA (the last note) is exactly double of that of the frequency of Sa (this first note). So, an Octave is actually the frequency band between Sa and SA.

Now considering the capabilities of human biology, human Ears cannot differentiate clearly between very small changes in the frequencies and hence to make a clear difference in the sounds, there must be a minimum difference between two sounds, and this is how Srutis are defined. Srutis divide the frequencies in an Octave into 22 distinct parts and each Sruti represents a relation between its previous Sruti and the next Sruti.

It is important to understand that Srutis represent a relation between the previous and next Sruti and hence no matter which frequency an Octave starts the Srutis are going to divide it into 22 relative parts.

Also, Srutis are not equidistant, which means two Srutis can have a variable frequency difference but the proportion in each octave is supposed to be same.
Here is the list of divisions of Srutis in Hindustani Classical Music.

Sa Re Ga Ma Pa Dha    Ni
4  4  3  2  4   3     2

Here is a full list of all the Srutis and their Carnatic Music names.
(May be just bookmark it for reference)

​Sruti Name
​Sign​Carnatic Name
​22​SHADJA TARA​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​​S​Shadja Tara
​21​Tivra Ni​N+
​20​SHUDDHA NI​N​Kakali Ni
​19​Komal Ni​n​Kaisiki Ni
​18​Ati Komal Ni​n- 
​17​SHUDDHA DHA​D​Chatuhasruti Dha 
​16​Trisruti Dha​D-
​15Komal Dha​d​SHUDDHA DHA
​14Atikomal Dha​d
​12​Tivratara Ma​m+
​11​Tivra Ma​m​Prati Ma
​10​Ekasruti Ma​M+
​09​SHUDDHA MA​M​Shuddha Ma
​08​Tivra Ga​G+
​07​SHUDDHA GA​G​Antara Ga
​06​Komal Ga​g​Sadharana Ga
​05​Atikomal Ga​g-
​04​SHUDDHA RI​R​Chatuhsri Ri
​03​Madhya Ri​R-
​02​Komal Ri​r​Suddha Ri
​01​Atikomal Ri​r-
​0​SHADJA​S​Shadja Madhya 

There is a significant similarity between Hindustani Classical Music and the ancient Greek Music culture. But a major difference between Indian and Greek musicology is that in Greece the Octave was divided into 24 Srutis so the proportion were also different.

I hope it is now clear what Sruti means, let me know if I missed something as I would love to listen your feedback.
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10 Thaats in Hindustani Classical Music: Most Important

10 Thaats in Hindustani Classical Music

What are Thaats? 

In simple words, Thaats are a way to classify various ragas into groups based on which Swaras are used in a specific Raga. When thinking about it you might think that Thaats and Ragas were created at the same time but contrary to the intuition, the Ragas existed long before the Thaats and later Thaats were created to classify the Ragas.

The question now you can ask, then who created Thaats? Well, Thaats were created by a musicologist name Vishnu Narayan Bhatkhande (1860-1936) and his first ideas were inspired by the Mela System of Carnatic Music from South India. The Mela System or more fully, a Swaramela System represents a group or collection of Swaras which are compatible with each other in the pitches so that when sung together they sound wonderful.

Properties of Thaats

A Classification System for Ragas: 

Since Thaats are not actually Ragas but rather they are a classification system, obviously, they are not supposed to be sung by a singer. It is like in a school, if the students are represented by class VI and class VII, then these classes are not supposed to be taught by a teacher, instead, it is the students who are taught by the teacher. Or another example can be, if we make a house based on the blueprint then we don’t live in a blueprint but we live in a house. (Hope it is clear). Thaats are also represented by “Mode” which is nothing but a specific scale in Hindustani Classical Music.

Thaats always have 7 Notes (Pitches): 

Let us not forget that in Indian Classical Music notes of an octave have names like this:

Sa Re Ga Ma Pa Dha Ni SA 

I will use the notation for notes like this:

Komal Swara (flat notes): All small caps

Tivra Swara (sharp): Swara+

Now of course there are some Komal and Tivra version of these Swaras which are represented as follows:

  • Flat Re: re
  • Flat Ga: ga
  • Flat: Dha: dha
  • Flat Ni: ni
  • Tivra Ma, Ma+

So now including these variations of Swaras we have in total 12 Swaras like this:

Sa,  (re Re), (ga Ga), (Ma Ma+) Pa (dha Dha) (ni Ni) 

Having these 12 notes, any combination of 7 notes out of 12 notes will represent a Thaat if it follows the following rule:

RULE: Any parent scale can have just one note from the following pairs (re, Re), (ga, Ga), (dha, Dha), and (ni, Ni). 

So now if we do some Maths then we have the following possibilities:

1 x 2 x 2 x 2 x 1 x 2 x 2 = 32

This number 32 represents a total number of Thaats which were initially proposed by Bhatkhande.
But later, he decided to only have 10 main Thaats which cover almost all the Ragas and hence today we only learn about 10 Thaats by their names.

Thaats have only Aroh Sequence: 

I think this is very clearly understood that since Thaats are not supposed to be sung, they only have Aroh sequence.

Both Version (Note and Semintone) of a Swara is Not Allowed

Although we have ga and Ga or Ma and Ma+, but in any Thaat, both versions of the Swara are not allowed. Now if you pay attention, you will notice a pattern that this rule actually removes the possibility of having Swaras which are half tone (semitone) apart. Which is a stricter rule than generally found in Mela System.

For example, an acceptable classification for Mela System like this

Sa re Re Ma+ Pa dha Dha SA

is completely not accepted in Hindustani Classical Music as it contains notes which are half note apart (Violation is marked in Red). Also, it violates the rule define before.

Which Ragas belong to which thaats (Examples). 

The main 10 (and not 32) Thaats which were proposed by Bhatkhande are named after the most popular Raga which belongs to it. Here are the 10 Thaats and some Ragas which belong to it.

Bilawal (Ionian mode): Sa Re Ga ma Pa Dha Ni SA

Morning: Raga Alhaiya Bilawal, Raga Bilawal
Evening: Raga Durga
Night: Raga Bihag, Raga Hamsadhwani

Khamaj (Mixolydian mode): Sa Re Ga ma Pa Dha ni SA

Evening: Raga Desh, Raga Khamaj
Night: Raga Gorakh Kalyan, Raga Champakali, Raga Jog, Raga Rageshree, Raga Saraswati, Raga Tilak Kamod

Kafi (Dorian mode): Sa Re ga ma Pa Dha ni SA

Morning: Raga Asavari, Raga Jaunpuri
Afternoon: Bhimpalasi
Evening: Raga Kafi, Raga Patdeep
Night: Raga Bageshree, Raga Chandrakauns, Raga Pilu, Raga Shivranjini

Asavari (Aeolian mode): Sa Re ga ma Pa dha ni SA

Morning Raga Asavari, Raga Jaunpuri
Night: Raga Adana, Raga Darbari

Bhairavi (Phrygian mode): Sa re ga ma Pa dha ni SA

Morning: Raga Bhairavi, Raga Komal Rishabh Asavari
Night: Raga Malkauns

Bhairav (double harmonic): Sa re Ga ma Pa dha Ni SA

Morning: Raga Ahir Bhairav, Raga Bairag, Raga Bhairav, Raga Jogiya, Raga Nat Bhairav, Raga Ramkali

Kalyan (Lydian mode): Sa Re Ga Ma Pa Dha Ni SA

Afternoon: Raga Shudh Sarang
Evening: Raga Bhopali, Raga Meru Bihag, Raga Yaman
Night: Raga Kedar

Marwa Sa re Ga Ma Pa Dha Ni SA

Dawn: Raga Bhatiyar, Raga Sohini
Evening: Raga Puriya Kalyan

Poorvi Sa re Ga Ma Pa dha Ni SA

Dawn: Raga Lalit
Afternoon: Raga Poorvi
Evening: Raga Puriya Dhanashree

Todi Sa re ga Ma Pa dha Ni SA

Morning: Gujari Todi
Afternoon: Raga Madhuvanti, Raga Multan

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