North Sumatra, South East Aceh in the Gayo highlands is an area of origin of the unique Saman dance. The dance was originally danced by 10 men, without the accompaniment of musical instruments. The musics produced by the voice of two group leader (syekh), clappinghands and pat chests. The lyrics are about islamic preach, ethics, epic etc. Syekh tasked also to give command of motion changes. This dance reportedly discovered and developed by Sheikh Saman, a scholar Gayo, although I think this dance seems older than that.
This dance now has spread throughout Aceh and Indonesia, performed by men and women. The dancers have to practice in earnest with full concentration because each dancer must be in sync with others.
Source wikipedia