Kecak, the dance with no instruments
The one thing to remember
No gamelan. No drums. The entire orchestra is a hundred men chanting cak.
A hundred voices instead of an orchestra
Almost every Balinese performance is carried by the gamelan, a bronze orchestra you feel as much as hear. Kecak throws it away entirely. Dozens of men sit in tight circles around a torch and chant interlocking rhythms, cak cak cak, layered against one another until the sound is a single living engine. There is no instrument on stage. If you see one performance in Bali, this is the one people never forget.
It tells the Ramayana
Inside the circle, the story is the Ramayana: Rama, his wife Sita, her abduction, and the white monkey general Hanuman who comes to the rescue and usually steals the show. You do not need to follow the plot to feel it. The chant carries the drama on its own, rising and cutting out dead silent at exactly the right moments.
It is younger than it looks
Here is the fact that surprises everyone: Kecak in the form tourists watch today took shape in the 1930s. It grew out of the sanghyang trance ritual, where chanting supported dancers in a trance state, and was developed into a performance piece for visitors, with the German artist Walter Spies among those involved. That does not make it fake. It makes it a living tradition that was still being invented within living memory, which is very Balinese.
The fire dance is a different thing
At many venues a fire dance follows the Kecak, where a performer walks barefoot through burning coconut husks, kicking up sparks. That is sanghyang jaran, a separate trance dance, not part of Kecak itself. Worth knowing so you can tell people what you actually saw.