(Public domain picture from Websters Dictionary 1911 Full size image)
Professional instruments are made from african hardwood, often ebony. The instrument uses a single reed which is held in the mouth by the player. The body of the instrument is mostly of uniform diameter until the bell is reached. The body is equipped with a complicated set of keys Boehm System and holes which allow the full musical scale to be reproduced. Clarinets are usually pitched in the key of B flat or A, as though there is a C clarinet, its tone is rather shrill. Clarinets exist in fact in every key though the next most common is the E flat and the Bass clarinet. At the large end there is a contrabass clarinet pitched two octaves below the standard model. The fixed reed and the uniform diameter give the instrument a configuration of a stopped pipe where use of an octave type key produces a one twelfth increase in pitch.
Clarinets are part of the normal orchestral make up. They are common in jazz and wind bands.