"Tro-u" is ancestral drum music that is played to invite ancestors to special sacred occasions at a shrine. For religious purposes, a priest or priestess would be present. There are fast and slow rhythms that can be called by the religious leader in order to facilitate communication with the spirit world. The bell rhythm is played on a boat-shaped bell in the north, but the southern region uses a double bell. The three drums must have distinct pitch levels in order to lock in.