What is Aadhara Shruthi? (Carnatic Music Tonic Explained)

To understand clearly what Aadhara Shruthi is, one must already know clearly what sound fundamentally is, and also know what is frequency & pitch. So, it is strongly recommended to read the blog about Sound, Frequency & Pitch before continuing with this one.

What is Shruthi?

The word Shruthi is used in many contexts. In this article, we are focusing on Shruthi as Aadhara Shruthi. 

1. Aadhara Shruthi is also very commonly referred to as just Shruthi. What is Aadhara Shruthi?
   • A reference pitch chosen by the artist based on their ability and convenience, that is aligned with the key note (Sa – Shadja) is called Aadhara Shruthi.  The other notes will be relative to the key note, here referred to as Aadhara Shruthi or Aadhara Shadja. 
   • Not every frequency (Hz) is noticeably different to human ears. So, humans have selected frequencies that are noticeably different from each other and made a corresponding chart (called Note-to-Frequency chart) to standardize this concept worldwide. We use those same Western pitch labels like C, C#, D etc. to indicate the frequency chosen as Aadhara Shruthi.
   • The artist chooses his or her own Aadhara Shruthi regardless of the composition (not the composer).
   • Ex: Suppose an artist has chosen their Aadhara Shruthi to be D# (according to the Note to Frequency chart as discussed earlier). It means, his Sa (Shadja) is sung in or tuned to D#. The other notes are relative to that Sa (Shadja). In this case, D# is referred to as the artist’s Aadhara Shruthi (or simply Shruthi).

How does a beginner choose their Aadhara Shruthi? What factors determine it? 

• Comfortable maximum range. That means it’s neither too high nor too low for the voice or the instrument in consideration. For ex: Typically, kids & female vocalists will have Aadhara Shruthi of G, G#, A or A#. Male vocalists will have Aadhara Shruthi of D, C#, C or B. Violins & flutes are usually tuned to D, D# or E as Aadhara Shruthi. 
• Generally, students under a Master’s guidance are naturally guided in the Master’s Aadhara Shruthi. 

2. Another context in which the word Shruthi is used here. Shruthi refers to the smallest perceived interval of pitch. As mentioned before, not every frequency (Hz) is noticeably different to human ears or more importantly, musically necessary or significant. So, in Carnatic music, the smallest perceptible pitch intervals in reference to any particular Aadhara Shruthi are called Shruthis. There are 22 Shruthis. You can read more about the 7 Notes, 12 Swarasthānās, and the 22 Shruthi system here.