The word bansuri originates in the Sanskrit bans [bamboo] + sur [melody]. There are two varieties of bansuri: transverse, and fipple. The fipple flute is usually played in folk music and is held at the lips like a whistle. Because it enables superior control, variations and embellishments, the transverse variety is preferred in Indian classical music.
Bansuri construction is a complex art. The bamboo suitable for making a bansuri needs to possess several qualities. It must be thin walled and straight with a uniform circular cross section and long internodes. Being a natural material, it is difficult to find bamboo shafts with all these characteristics, which in turn makes good bansuris rare and expensive. Suitable species of bamboo (such as Pseudostachyum) with these traits are endemic to the forests of Assam and Kerala.
After harvesting a suitable specimen, the bamboo is seasoned to allow naturally present resins to strengthen it. Once ready, a cork stopper is inserted to block one end, next to which the blowing hole is burnt in. The holes must be burnt in with red hot skewers since drilling causes the fibrous bamboo to split along the length, rendering it useless. The approximate positions of the finger holes are calculated by measuring the bamboo shaft’s inner and outer diameters and applying certain formulae. Flute makers have only one chance to burn the holes, and a single mistake ruins the flute, so they usually begin by burning in a small hole, after which they play the note and using a chromatic tuner and a drone called tanpura, gradually make adjustments by sanding the holes in small increments. Once all the holes are perfected, the bansuri is steeped in a solution of antiseptic oils, after which it is cleaned, dried and its ends are bound with silk or nylon threads for both decoration as well as protection against thermal expansion.
Indian music is played in 3 octaves — mandra (lower), madhya (middle), an taar (high) — with ornamentations such as meends (glides) and gamaks (oscillations).
Bansuris range in length from less than 12 inches (called muralis) up to about 40 inches (shankha bansuris). 20-inch bansuris are common. Another common and similar Indian flute played in South India is the venu, which is shorter in length and has 8 finger holes (this type of Indian flute is played by the Carnatic musician Shashank Subramanyam). The index, middle, and ring fingers of both hands are usually used to finger the six hole bansuri. For the seven hole bansuri, the little finger (pinky) of the lower hand is usually employed.