clarinet. Single-reed woodwind instr. with cylindrical tube developed c.1690 by J. C. Denner of Nuremberg, who, by adding 2 keys to the chalumeau, increased that instr.'s range by over 2 octaves. It was not playable in all keys until 1843 when Klose adapted the Boehm fl. key system to the cl. The first composer to use the cl. in a sym. was Mozart.

As the reed blocks one end of the tube, the pipe acts as a ‘stopped’ one, sounding an octave lower than it would have done if left open. Like other cylindrical tubes the cl. overblows at the interval not of its first upper partial, the interval of an octave (as the fl. and ob. do), but at its 2nd (the interval of a 12th). The notes of the instr.'s first octave are obtained in the normal way and the gap of a 5th before the overblowing begins has to be filled by additional side-holes which leave the tone weaker at this point and the fingering somewhat more awkward. All members of the family have great powers of pianissimo and of crescendo and diminuendo—greater than those of any other wind instr. Double, triple, and flutter tonguing are possible.

Varieties of cl. incl.:

(a) clarinet in C, B♭, or A—the normal treble instr. The existence of these 3 pitches was to enable the composer to use any key without creating undue difficulty for the player (see transposing instrument). The B♭ clarinet is a transposing instr., sounding a tone lower than written. The A clarinet sounds a minor 3rd lower than written. The C instr. is now not much used, on account of inferior tone, but figures in the scores of classical composers. It is not a transposing instr. (b) bass clarinet. Its range lies an octave below that of one of the above (usually of that of the B♭ instr.). It differs somewhat in shape, its lower end being curved upwards and ending in a bell, and its upper one continued by a tube bent downwards to reach the player's mouth. Except in military band mus. it is treated as a transposing instr., its mus. being notated either in the treble clef and a 9th higher than the sound (Fr. method), or in the bass clef a 2nd above the sound (Ger. Method). (c) high E♭ clarinet, a 4th above the B♭ instr. It is found in all military bands and occasionally figures in orch. scores, e.g. Richard Strauss's Alpensinfonie. It is a transposing instr., its mus. being notated a minor 3rd lower than the sound. (d) high D clarinet. This serves the same purpose as the E♭ cl., but is much rarer. It is a transposing instr., being written for a tone lower than the sound. R. Strauss uses it in Symphonia Domestica and with outstanding effect in Till Eulenspiegel. (e) alto clarinet—in E♭ and F. The E♭ is used in symphonic wind bands, concert bands, and cl. choirs. The F instr. is practically a modernized basset horn. Both are written for in the treble clef and are transposing instr. (f) pedal clarinet, or contrabass clarinet, or double-bass clarinet. Almost entirely a military band instr. Its part is written 2 octaves and a tone higher than the sound. (The word ‘pedal’ had no reference to any part of the construction and the origin of its use is not very clear.) (g) 3 obscure modern instr. related to the cl. family by possessing a single reed are the clarina, the heckelclarina or Heckelclarinette, and the Holztrompete. All were invented to represent the shepherd-boy's pipe in Act III of Wagner's Tristan und Isolde, but have not displaced customary use of the cor anglais.

Note that the old Eng. spelling ‘clarionet’ is obsolete.