Ravana hypnotises the chorus.
The kecak (cak) is based on the ancient dance chorus tradition. Men seated at the dead of night in circles around a large oil lamp chant the syllables “cak-kecak-cak” with immense strength and astounding rhythmic precision. The fast abdominal breathing and the bursting vocal of this gamelan svara or “voice orchestra” lead easily to hyperventilation and trance.
Meittinen, J.O. (2018) Kecak, In The Twentieth Century. Theatre Academy of the University of the Arts Helsinki https://disco.teak.fi/asia/the-twentieth-century-bali/