reed instrument, in music, an instrument whose sound-producing agent is a thin strip of cane, wood, plastic, or metal that vibrates as air is passed over it. The predecessor of these instruments is the Chinese sheng. Single-reed instruments have one reed that is either free or beating. Free reeds, such as those in the reed organ, accordion, concertina, and harmonica, do not overlap the air passage; they are generally of metal. Beating reeds, such as those used in organ pipes and in the clarinet, strike the edges of the aperture while vibrating. Double-reed instruments, such as the shawm, oboe, bassoon, and English horn, have two reeds facing each other, between which air is forced into the instrument; thus the reeds are set vibrating.