Kecak (pronounced: "KEH-chahk", alternate spellings: Ketjak, Ketjack, and Ketiak), a form of Balinese music drama, originated in the 1930s and is performed primarily by men. Also known as the Ramayana Monkey Chant, the piece, performed by a circle of 100 or more performers wearing checked cloth around their waists, percussively chanting "cak" and throwing up their arms, depicts a battle from the Ramayana where monkeys help Prince Rama fight the evil King Ravana. However, Kecak has roots in sanghyang, a trance-inducing exorcism dance.
In the 1930s Wayan Limbak worked with German painter Walter Spies to create the Kecak from movements and themes in the traditional sanghyang exorcism ritual and the portions of the Ramayana. This collaboration between artists worked to create a dance that was both authentic to Balinese traditions but also palatable to Western tourist's narrow tastes at the time. Wayan Limbak popularized the dance by travelling throughout the world with Balinese performance groups. These travels have helped to make the Kecak famous throughout the world. (Source http://www.wikipedia.org)