articipants of the capoeira dance or game stand in a circle around the capoeiristas singing a call and response song while musicians play instruments. What is the single stringed instrument called that sets the tempo of the dance?

The istrument is called Berimbau

Explanation:

This instrument was taken by Angolan slaves to Brazil where it was used to accompany dance/fight / acrobatic sport called capoeira. The berimbau is a fundamental element in capoeira, being revered by capoeiristas before starting a game. Some consider it a sacred instrument. He controls the capoeira wheel, dictates the pace and style of play.