The drum is a member of the percussion group of musical instruments. In the Hornbostel-Sachs classification system, it is a membranophone. Drums consist of at least one membrane, called a drumhead or drum skin, that is stretched over a shell and struck, either directly with the player’s hands, or with a percussion mallet, to produce sound. There is usually a resonance head on the underside of the drum, typically tuned to a slightly lower pitch than the top drumhead. Other techniques have been used to cause drums to make sound, such as the thumb roll. Drums are the world’s oldest and most ubiquitous musical instruments, and the basic design has remained virtually unchanged for thousands of years.
Drums may be played individually, with the player using a single drum, and some drums such as the djembe are almost always played in this way. Others are normally played in a set of two or more, all played by the one player, such as bongo drums and timpani. A number of different drums together with cymbals form the basic modern drum kit.
Drums are usually played by striking with the hand, a beater attached to a pedal, or with one or two sticks with or without padding. A wide variety of sticks are used, including wooden sticks and sticks with soft beaters of felt on the end. In jazz, some drummers use brushes for a smoother, quieter sound. In many traditional cultures, drums have a symbolic function and are used in religious ceremonies. Drums are often used in music therapy, especially hand drums, because of their tactile nature and easy use by a wide variety of people.