Udukku (or Udukkai), is an hour glass shaped instrument of ancient Tamil origin. The Udukku is used extensively at temples, during prayers and folk music. It is regarded as a very auspicious instrument which is said to be the source of all sound in the universe. Being held on the right hand of Lord Shiva it is symbolic of creation and the sound produced by it is said to be the source of the Pranava Manthiram, the AUM.
 
The hour glass shaped body ranges in length of about
8 – 10 inches with a diameter of about 6 – 8 inches at either side. The instrument traditionally was made of hardened clay (sometimes hardened by firing in a kiln). Modern variants of the body include wood that is hollowed out from a single block of Jackfruit wood, usually painted red to resemble the finish colour of the clay, or a single cast piece (or two joint cast pieces) of brass.
 
 

Very thin layer (the outer membrane) of goat skin is stretched across flat, but slightly curvy, wooden hoop and attached to the two sides of the body loosely using small strings. One side (non playing side or the left head) of the Udukku has one or two snares, made of curled metal wire, attached across it to produce a more resonating “brighter” sound.

A cloth strap is then wrapped around the strings at the centre of the body by which the Udukku is held at either the top or bottom of the clasped hand.

The right head, the playing side, is played with the right hand, front part of the palm, and fingers. While playing the left, or the holding, hand aids to vary the pitch by squeezing or relaxing the cloth strap and intern the attached strings. When the Udukku is held above the clasping hand one or two of the fingers can be lifted out to grasp the strings directly (as supposed to the strap).

When the Udukku is held below the clasping hand one or two of the fingers are used to put pressure on the strap directly. Grasping or applying pressure with fingers are done so as to have better control of the pitch modulation.

In addition to producing rhythmic notes, the pitch of the Udukku can be regulated to mimic the tone of the human speech (vocal notes). Those that are proficient in playing the Udukku can make it “sing” to songs.