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.

Any musical wind instrument that sounds when the player's breath or air from a wind chamber causes a reed (a thin blade of cane or metal) to vibrate, thereby setting up a sound wave in an enclosed air column or in the open air. Reed pipes have single or double reeds. A double reed, as in the oboe or bassoon, consists of two cane blades tied together that beat against each other. A single reed may hit against a frame (beating reeds), as in the clarinet or saxophone, or it may vibrate freely through a closely fitting frame (free reeds), as in a harmonica or accordion. Beating reeds in woodwind instruments depend on the pipe's sounding length (as determined by the fingering) to determine the pitch. Free reeds have their own single pitch, determined by their thickness and length. Seealso English horn; shawm.

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