A
bell is a simple
idiophone percussion instrument. Although bells come in many forms, most are made of
metal cast in the shape of a hollow
cup, whose sides form a
resonator which vibrates in a single
tone upon being struck. The strike may be made by a "clapper" or "uvula" suspended within the bell, by a separate mallet or hammer, or—in small bells—by a small loose sphere enclosed within the body of the bell.