Various bells are a common part of royal regalia, and were used in secret societies. They are usually made of iron, or in Islamic orchestras of the north, of bronze. Struck gourds, placed on a cloth and struck with sticks, are a part of women's music, as well as the bòòríí cult dances. Sometimes, especially in the north, gourds are placed upside-down in water, with the pitch adjusted by the amount of air underneath it. In the south-west, a number of tuned gourds are played while floating in a trough.