The kora is made from a large gourd known as a calabash.  It is cut in half, emptied and dried and covered with animal skin. There are 21 strings which were originally made from animal hide and gut but now nylon line is used.  Some koras, particularly in the Casamance area of southern Senegal and in The Gambia, have an extra bass string so the 22 string kora is common there. Some kora players do use more, but this is relatively unusual.