or Sundanese in origin and style. It is developed predominately from rural folk forms and traditions as a purely indigenous form. The rise of cassettes and films has led to the popularity of the musical form of jaipongan. It has spread from its home in West Java's Sunda, to greater Java and Indonesia. It can be seen as many regional varieties of gong-chime performance found through much of Indonesia. Ketuk tilu is its biggest influence, as a traditional Sudanese musical entertainment form. Gong-chime performance is characterized by such features as: use of an ensemble dominated by idiophones, metallophones and knobbed gongs. It is a stratified polyphony, with lower-pitch instruments playing parts of lesser density and all parts are structured colotomically around time-cycles. This can be found in traditional Indonesian gamelan. There is improvisation on certain instruments. The modes used are grouped into two broad types: slendro and pelog. Ronggeng probably has existed in Java since ancient time, the bas reliefs in Karmawibhanga section on Borobudur displays the scene of travelling entertainment troupe with musicians and female dancers. The cassette industry and its boom in Indonesia helped popularize jaipongan greatly and promoted regional styles rather than hurt them. The song repertoire of jaipongan is varied, and that is why it is better understood as an intertwined performance style of music and dance. Many songs are associated with ketuk tilu or other wide reaching regional varieties, not traditional gamelan. It consists of songs of more recent origin often composed for jaipongan. Song topics vary, encompassing amatory, moralistic, bawdy, topical and spiritual subjects, often emphasizing grass roots culture. Instrumentation and choreography Jaipongan is "a more slick and expanded version of ketuk tilu". Jaipongan takes much of its instrumentation from ketuk tilu ensembles. The ketuk tilu group is composed of pot-gongs. Besides the core three main kettle gongs (ketuk means to knock (or knocking sound), but in this case refers to the three gongs; while tilu means three), the instruments include a rebab, a small upright bowed instrument, also known as a spike fiddle, other small gongs — a hanging gong and two iron plates, and two or three barrel drums. The traditional singer is female or a sinden, but also dances and invites men to dance with her sensually, so it is assumed she is a prostitute or ronggeng. The idiophonic accompaniment of jaipongan may also include a few saron or a gegung