Before the first song begins, a drone is set going, and it usually continues until the last note. It sounds the tonic, Sa, usually with Pa or Ma, and everything else in the performance is heard against it. The drone itself changes very little.
What the tanpura plays
The traditional source is the tanpura, often called the tambura in South India. It is a long-necked lute, usually with four strings, plucked one after another in a slow, unbroken cycle. It plays no melody. A common tuning is Pa in the lower octave, two strings at middle Sa, and a Sa an octave below. In ragas that omit Pa, the first string may be tuned to Ma instead. Some Hindustani musicians use other variants for particular ragas, including a tuning to Ni. Practice depends on the tradition, the raga and the musician.
Where the buzz comes from
Heard up close, the drone has a bright, buzzing shimmer. The strings pass over a broad, slightly curved bridge, and a thin cotton or silk thread placed between each string and the bridge sets how they touch. As a string vibrates, it grazes the bridge. This produces a full series of overtones, an effect musicians call jawari. The physicist C. V. Raman described it in 1921, and acoustic researchers have studied it ever since. Adjusting the thread is a skilled job, and without the grazing contact the tone turns dull.
Tuning to it
The drone is tuned to the principal performer’s Sa, and the accompanists match it. Researchers Asoke Kumar Datta and colleagues note that practicing with the tanpura helps singers hear consonance and place their notes accurately. The violinist L. Ramakrishnan has described keeping everyone on stage aligned with that pitch as his biggest challenge.
Acoustic and electronic
Many concerts now use an electronic drone, often called a sruti box, instead of or alongside a tanpura. The engineer G. Raj Narayan demonstrated an electronic tanpura at the Music Academy, Madras, in 1979. Writing in 2023, Lakshmi Anand found that most Carnatic musicians she asked preferred the acoustic instrument, but valued electronic ones for practice, travel and extra support on stage.
At the next concert, listen to the drone alone for a moment before the music starts. Then notice how a long, steady Sa or Pa from the singer seems to settle into it.
For how notes take on character within a raga, see A Raga Is More Than a Scale. For more ways into a performance, see Start Listening.
