Bak A percussion instrument used in Dangak and Hyangak since Unified Silla to indicate the end or beginning of a section or change in dance movements.

The gourd is a musical instrument made of six pieces of wood. It is a conducting percussion instrument that informs and directs the progress of music and dance. There are records of use since Unified Silla, and during the Goryeo Dynasty, there were Daeakgwanhyeonbang and Songbakeopsa

Among the old sheet music, a beat is usually struck at the beginning of the Janggu beat or at every verse in the editorial. And in Jeongjae, not only the beginning and the end of the dance, but also the beginning and the end of the change in the formation and movement of the dance, the Changsa, the slogan, the cheer, and the death At the beginning and end of the back, beat the beat without falling into the music. In addition, the music of the ritual ceremonies also beats all the musical procedures, such as writing and music.