A reed is a thin strip of material which vibrates to produce a sound on a musical instrument. The reeds of most woodwind instruments are made from Arundo donax ("Giant cane") or synthetic material; tuned reeds (as in harmonicas and accordions) are made of metal or synthetics.
Single reeds 
Single reeds are used on the mouthpieces of clarinets and saxophones. The back of the reed is flat and is placed against the mouthpiece, the rounded top side tapers to a thin tip. These reeds are roughly rectangular in shape except for the thin vibrating tip, which is curved to match the curve of the mouthpiece tip. All single reeds are shaped similarly but vary in size to fit each instrument's mouthpiece. Reeds designed for the same instrument may look identical to each other, but may vary in thickness ("hardness" or "strength"). Hardness is generally measured on a scale of 1 through 5 from softest to hardest. This is not a standardized scale and reed strengths vary by manufacturer. The thickness of the tip and heel and the profile in between affect the sound and playability. Cane of different grades (density, stiffness), even if cut with the same profile, will also respond differently.
Double reeds 
Double reeds are used on the oboe, oboe d'amore, english horn, bassoon, contrabassoon, sarrusophone, shawm and bagpipes. They are typically not used in conjunction with a mouthpiece; rather the two reeds vibrate against each other. However, in the case of the crumhorn, bagpipes, and Rauschpfeife, a reed cap that contains an airway is placed over the reeds and blown without the reeds actually coming in contact with the player's mouth. Reed strengths are graded from hard to soft.
Free reeds 
There are two types of free reeds: framed and unframed. Framed free reeds are used on ancient Asian instruments such as the Chinese shēng, Japanese shō, and Laotian khene, and modern European instruments such as the harmonium or reed organ, harmonica, concertina, bandoneón, accordion, and Russian bayan. The reed is made from cane, willow, brass or steel, and is enclosed in a rigid frame. The pitch of the framed free reed is fixed.
The primitive bullroarer is an unframed free reed; it consists simply of a stone or board of wood tied to a rope which is swung around through the air to make a whistling sound. Another primitive unframed free-reed instrument is the leaf (the bilu), used in some traditional Chinese music ensembles. A leaf or long blade of grass is stretched between the sides of the thumbs and tensioned slightly by bending the thumbs to change the pitch. The tone can be modified by cupping the hands to provide a resonant chamber.
Most reeds for woodwind instruments are made from cane, but synthetic reeds are used by a small number of clarinetists, saxophonists, and double reed players, as well as by bagpipers. Synthetic reeds are generally more durable than their natural counterparts and do not need to be moistened prior to playing. Many players consider them to have inferior tone quality.
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.
Commercial vs. handmade 
Musicians originally crafted reeds from cane using simple tools, a process which was time-consuming and painstaking. Specialized tools for cutting and trimming reeds by hand reduce the time needed to finish a reed. 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.
"Reed players" 
Especially in musical theatre orchestras, woodwind players are commonly referred to as "reed players" or "reeds". These players are not restricted to one particular woodwind instrument group, but play ("double on") several different instruments. (Although the flutes are not reed instruments, they are included as well.)
There are usually only four or five reed players in a pit orchestra who perform on all woodwind instruments (flute, oboe, clarinet, bassoon, saxophone). A basic reed part usually has three or four instruments (flutes, clarinets and saxophones being the most common), but can include up to eight instruments, such as the "Reed 3" part in Bernstein's West Side Story, which calls for the player to use piccolo, flute, oboe, English horn, clarinet, bass clarinet, and tenor and baritone saxophones. Through intricate doubling, the arranger can simulate the sound of a much larger woodwind section. (The West Side Story woodwind section would require twelve "classical" players instead of five "reed" players.)
See also 
- Reed aerophones
- Free-reed instrument
- Mouthpiece (woodwind)
- Uilleann pipes reed-making workshops in Ireland.
- Henry Doktorski, "The Classical Squeezebox: A Short History of the Accordion and Other Free-Reed Instruments in Classical Music," The Classical Free-Reed, Inc. (1997).