Construction
The clarinet is a single-reed woodwind instrument, composed of a cylindrical tube of wood, generally cocus, terminating in a small bell. The beak shaped mouthpiece of wood or ebonite (which does not crack of suffer from moisture) fits into a socket in the upper part of the tube. To this is bound by a ligature, adjusted by two screws, a thin and flattened piece of reed, which the player sets vibrating by blowing into the mouthpiece, thus producing the rich, mellow sounds peculiar to the clarinet family.

Production of Sound
The notes are formed by means of nine open finger holes and nine closed by keys raised by levers. These, with the bell, produce the 19 semitones which constitute the fundamental scale of the clarinet; the rest of its compass is obtained by a key contrivance which, determining a node in the bore, raises the pitch of the instrument a twelfth. The flute, oboe and similar instruments give the octave or first harmonic when overblown, because they act like open pipes, which give the entire harmonics series. In the clarinets, however, the effect is that of a stopped pipe, closed at one end, because of the size and strength of the reed which is said to govern the tube. Stopped pipes give only half the harmonics, thus causing a soft and mellow tone. In tubes, a node is the point where the air vibrates with constant pressure, as at the end of the tube or opposite an opened keyhole. In the oboe, in which the reed always vibrates with the air volume, the reed is at the point of maximum change in pressure, called the ventral segment. In the clarinet, however, the reed vibrates against the direction of the air vibrations, as it vibrates only half as fast as the oboe reed in the same sized pipe. The clarinet reed merely doubles the same air-condition that comes up the tube to it, either condensation or rarefaction. Thus it has the effect of being halfway between the node and the proper position of the ventral segment. As no ventral segment can form at the reed of a clarinet, it follows that subdivision of the air-column into even fractions is impossible, and every other overtone of the series remains silent.

Quality of Tone
There are three principal treble clarinets, tuned to C, B-flat and A major. The quality of tone of the three clarinets vary greatly; that of the C being shrill, hard and less powerful than that of the other two; it is on that account little used, except for open-air music. The B-flat clarinet is remarkable for great brilliancy and sonorousness, and is the most generally used, especially as a solo instrument. The A clarinet is sweet and mellow. Composers take these differences of tone as well as those of pitch into consideration when writing for the instrument.

Origin
The name of the instrument is derived from the Italian clarion and English clarion (meaning trumpet.) Its medieval prototype is probably, as is common with all reed instruments, the shalmey or shawm. This was in its most primitive form a plain reed, called by the Romans calamus, which gave its name to the lowest register of the modern clarinet. Roman pifferari and Italian shepherds still use a similar reed-pipe or shalmey. The clarinet has only been known as such since about 1690, when it is said to have been invented by Johann Denner of Nuremberg.