What are the Dagbamba drummers called and how do they transmit their art?

An Earthwork is defined as a work that:

a. Large works that feature the Earth as a core subject matter b. Outside sculptures c. Paintings that use organic materials d. A large outdoor work in which the earth itself is the primary medium

An ere ibeji is made when

a. a contract is agreed upon. b. a youth is initiated into adulthood. c. a woman cannot conceive children. d. a twin dies.