Shruti

“Shruyate iti shruti”, as described in ancient texts, means “what is heard”(as well as understood).

In our Indian classical music, going by the above definition, the smallest interval of pitch that is perceived through our ears is “Shruti”.

Pitch: It is the sound of a note, as comprehended by human ears. So pitch of a note is either high or low based on the frequency. The higher the frequency of the note, the higher the pitch. So, if we consider a range of sound, pitch is the position of a single sound.

This pitch is measurable in Hertz (Hz), which is also the frequency of that note. Thus the notes on a scale are defined by their respective frequencies. High frequency, high pitch and low frequency, low pitch.

Interval: the difference between two pitches.

Saptak or Scale is the series of 7 notes Sa Re Ga Ma Pa Dha Ni. The saptak in which songs are usually composed is the Madhya Saptak or Middle Octave. Same notes or swaras with lower frequencies below Sa form the Mandra Saptak or Lower Octave. And when sung with higher frequencies than Madhya Saptak swaras these notes form the Taar Saptak or Higher Octave.

   .Sa .Re .Ga .Ma .Pa .Dha .Ni Sa Re Ga Ma Pa Dha Ni Sa` Re` Ga` Ma` Pa` Dha` Ni`

Bharat Muni’s Natyashastra, one of the oldest Sanskrit texts and first of its kind, dedicated to every aspect of performing arts(dance, drama, music), contains the exact and most accepted explanation of Shruti:

“ChatushChatushChatushchaiva; Shadaj Madhyam Pancham;

DvaiDvai Nishaad Gandhaarou; Tistri Rishabh Dhaivato”

(There are four Shrutis each for Shadaj(Sa), Madhyam(Ma), Pancham(Pa), two Shrutis each for Nishaad(Ni) and Gandhaar(Ga) and three shritus each for Rishabh(Re) and Dhaivat(Dha) swaras).

Explaining it further, it means that Shadaj is placed at a distance of 4 shrutis from its previous note nishaad of mandra saptak or lower octave. Similarly, Rishabh is placed 3 shrutis after Shadaj and so on. Thus the number of Shrutis recognized in an octave becomes 22.