The tanpura is a fretless stringed instrument used to produce the atmospheric drone that is ubiquitous in northern Indian classical music. In the southern parts of India, a smaller, lower-quality variation known as the tambura is common. Traditionally, the tanpura has only four strings, though five and six-stringed tanpuras exist. Typically, the middle two strings are tuned to a raga's middle-octave tonic, the fourth string is tuned to a bass-octave tonic, and the first string is tuned to the dominant.
The tanpura's upright length of 3-5 feet makes it impossible to miss at an Indian classical music concert. The tanpura is played seated, with arms bent upward to pluck the strings on the high neck. It is plucked very slowly with the middle and index fingers, providing atmosphere, not rhythm.
The resonance chamber at the bottom of the tanpura, called a tumba, is made of dried gourd (often pumpkin). The tumba creates a very rich, sonorous sound. The long neck is made of a wood such as jackwood. The bridge is made of curved bone. The metallic strings are cushioned by silk or cotton thread that rubs against the bridge, creating a buzzing sound unique to the tanpura.