श्रुति

Shruti comes from the Sanskrit root shru, to hear. Its most ancient meaning is that which has been heard — specifically, that which has been heard from divine sources and passed down through the ears of sages and students in the oral Vedic tradition. The four Vedas, the Upanishads, and the Brahmanas are shruti — not composed by human authors but revealed, heard, and transmitted. This is distinct from smriti (that which is remembered), the category for texts composed by human sages. The distinction between shruti and smriti is one of the most fundamental in Hindu textual tradition: shruti is heard directly from the divine; smriti is remembered and composed.

In music, shruti names something entirely different but with the same essential quality of precision in hearing. The 22 shrutis are the microtonal intervals into which the Indian octave is theoretically divided — gradations so fine that many are smaller than the semitones of Western equal temperament. The ancient theorist Bharata, in the Natyashastra, described the shrutis through the experiment of the two vinas: two identically tuned string instruments are compared, with one changed step by step through all the positions of the scale, to determine by the ear alone which intervals produce which qualities of consonance, dissonance, and neutral feeling. The result is a taxonomy of 22 positions based on what trained ears can reliably distinguish.

The relationship between the seven svaras and the 22 shrutis is one of the central technical problems of Indian musicology. The svaras are broad categories; the shrutis are their fine structure. Each svara occupies two, three, or four shruti positions; the specific shruti position a performer lands on within a svara range is part of what gives a raga its characteristic color. A tivra (sharp) Ga and a shuddha (natural) Ga are a svara apart; the fine inflection of a singer's Ga within the shuddha range — landing slightly higher or lower within that zone — is a shruti distinction, and it is precisely this level of precision that connoisseurs listen for.

In contemporary Indian classical music, the shruti box — a small keyboard instrument with reeds that sustains a continuous drone — is the standard tool for establishing the Sa and Pa drone against which a performer calibrates their microtonal pitch. The drone makes the shruti system audible: against its sustained tone, even slight deviations in the performer's pitch are immediately perceptible to trained ears. The name shruti box is a daily reminder, in every practice room and concert hall, that Indian music is fundamentally a practice of acute hearing — that the entire system, from the Vedic revelation to the microtonal scale, is built on the discipline of listening well.