Indian folk and tribal dances range from simple, joyous celebrations of the harvest seasons to ritualistic dances to propitiate demons and invoke spirits. Some dances are extremely simple with a minimum of steps or movements, but most are very vigorous and lively. The costumes are generally flamboyant with extensive use of jewellery by both the sexes. Tribal dancers of northeast India wear exotic head-dresses of feathers and animal relics, ornaments of beads and shells. Some dances are performed exclusively by men and women, but most have them dancing together. Nearly all involve singing by the dancers.