Drum, musical instrument of the percussion family, common to most cultures. It consists of a shell, cylindrical or conical, with a membrane, or skin, stretched over one or both ends. The skin is struck with the hand or with sticks. The principal drum in the symphony orchestra is the kettledrum, or tympanum, whose pitch can be adjusted by the tightening or loosening of the membrane. Other orchestral drums include the tenor, snare, and bass drums and the tamborine. Snares are important in popular maintaining rhythm in popular marching music.