REED INSTRUMENTS, a class of wind instruments in the tubes of which sound-waves are generated by the vibrations of a reed mouthpiece. Reed instruments fall into two great classes: (I) those blown directly by the breath of the performer, who is thus able to control more or less the character of the expression; (2) those in which the wind supply is obtained by mechanical devices, such as the bag of bagpipe instruments or the bellows of such keyboard instruments as the organ and harmonium.
Directly-blown reed instruments comprise the section of mod ern wind instruments known as the "wood wind," with the excep tion of flute and piccolo ; and they are classified according to the kind of reed vibrator of which the mouthpiece is composed. There are three kinds of reed mouthpieces: (I) the single or beating reed; (2) the double reed; (3) the free reed, all of which perform the function of sound-producer. (For illustration see FREE REED VIBRATOR.) The reed used consists of a thin tongue or strip of reed, cane or some elastic ma terial, thinned gradually to a deli cate edge. It is adapted to the tube in such a manner that when it is at rest the opening at the mouthpiece end of the tube con sists only of a very slight aper ture or chink, which is periodi cally opened and closed by the pulsations of the reed when acted upon by the compressed breath of the player. This principle is common to all reed mouthpieces, and the difference in timbre is in a measure due to the manner in which the pulsations are brought about and the degree of elasticity permitted.
The single or beating reed consists of a single blade bevelled at the edge and placed over a table or frame communicating with the main bore of the instrument, against which it beats, causing a series of pulsations. The single reed is common to all the mem bers of the clarinet family, consisting, besides the clarinet, of the basset-horn or tenor, and of the bass and pedal clarinets; of the batyphone, an early bass clarinet, and of the saxophone. The an
cient Greek aulos (q.v.) was also undoubtedly used with a beating reed during some period of its history.
The double reed consists of two blades of reed or other suitable material tightly bound together by many turns of waxed silk, so that above the constriction the tube formed by the two blades has an oval section, while below, where it communicates with the main bore of the instrument, it is strictly cylindrical. The chink in this case is thus formed by two thin walls of reed of equal elas ticity (see OBOE, BAssooN). The double reed is common to the members of the oboe family, consisting, besides the oboe, of the cor anglais or tenor, of the fagotto or bassoon, and of the contra fagotto or double bassoon ; and it is also used in the sarrusophone family, instruments of brass but classed with the wood wind on account of the mouthpiece and fingering.
The free reed is not represented among members of the modern wood wind, and, as adapted to a directly-blown instrument, only finds application in the Chinese cheng, the prototype of the har monium, and in the mouth-organ or harmonica.
The reed in wind instruments produces a peculiar tone quality to which it has given its name; it varies in the three different kinds of mouthpieces without losing its fundamental reedy timbre.
For reed instruments of the second class, viz., those indirectly blown by mechanical means, see under the names of the individual instruments—BAG-PIPE, CONCERTINA, HARMONIUM, ORGAN, etc.