Keplok is a style of clapping

Clapping

A clap is the sound made by striking together two flat surfaces, as in the body parts of humans or animals. Humans clap with the palms of their hands, often in a constant drone to express appreciation or approval , but also in rhythm to match sounds in music and dance...

 used in Javanese gamelan

Gamelan

A gamelan is a musical ensemble from Indonesia, typically from the islands of Bali or Java, featuring a variety of instruments such as metallophones, xylophones, drums and gongs; bamboo flutes, bowed and plucked strings. Vocalists may also be included....

. The clapping is in a specific interlocking rhythmic pattern and is performed by the gerong

Gerong

Gerong is the Javanese verb meaning "to sing in a chorus." Penggerong is the proper name of a member of the chorus, but often the word gerong is used to refer to the unison male chorus that sings with the gamelan. The chorus or the melody may also be called the gerongan.The gerong generally sings...

 when they are not singing. It is usually associated with the lively ciblon (Surakarta) or batangan (Yogyakarta) drumming. Usually one person claps on the on-beats while another claps on the off-beats, and then another pair clap a similar pattern at half the tempo. This interlocking pattern is similar to the imbal

Imbal

Imbal or imbalan is a technique used in Javanese gamelan. It refers to a rapid alternation of a melodic line between instruments, in a way similar to hocket in medieval music or kotekan in Balinese gamelan....

 patterns played on the saron

Saron (instrument)

The saron is a musical instrument of Indonesia, which is used in the gamelan. It typically consists of seven bronze bars placed on top of a resonating frame . It is usually about 20 cm high, and is played on the floor by a seated performer...

. Keplok is often performed along with senggakan.