Bira is an all-night ritual, celebrated by Shona people from Zimbabwe in which members of an extended family call on ancestral spirits for guidance and intercession.
The attendees at a ceremony participate in singing, dancing and hand clapping. The two mbira players are joined by a player on a pair of gourd shakers (hosho), which emphasize the underlying triplet beat. The mbira playing and singing are all improvised off the familiar basic patterns, resulting in a constantly changing polyphonic texture.
In this ceremony, music that was favored by the ancestors when they were alive is used to summon the spirits to possess living mediums; thus the religious belief system helps to preserve older musical practices.