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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The most obvious variation in reeds designed for the same instrument is a variation in thickness ("hardness" or "strength"), generally measured on a scale of 1 through 5 from softest to hardest. This is not a standardized scale and reed strengths vary between manufacturers. The thickness of the tip and heel and the profile in between also affect the sound and playability. Cane of different grades (density, stiffness), even if cut with the same profile, will also respond differently.
One example of the unframed reed is the primitive bullroarer; it consists simply of a stone or board of wood tied to a rope which is swung around and around through the air. It makes a whistling sound. Another primitive unframed free-reed instrument is the leaf (called bilu), which can be heard in some traditional Chinese music ensembles. A leaf, or a long blade of grass, is stretched between the sides of the thumbs and tensioned slightly by bending the thumbs, thereby raising or lowering the pitch. The tone of the instrument can be modified by cupping the hands so as to provide a resonant chamber.
Recent developments in synthetic reed technology have produced reeds made from synthetic polymer compounds
, and as technology in this area has progressed, synthetic reeds have gained more acceptance. Synthetic reeds are useful when the instrument is played intermittently with long breaks in between, during which time a natural reed might become dry.
The dizi, a Chinese transverse flute, has a distinctive kind of reed (a di mo), which is made from a paper-like bamboo membrane.
Today, nearly all players of single-reed instruments buy manufactured reeds, although many players adjust them by shaving or sanding. Some professionals make single reeds from "blanks", but this is time-consuming and can require expensive equipment.
Among double reed players, advanced and professional players typically make their own reeds, while beginners and students often buy reeds either from their teachers or from commercial sources.