The Clarinet is woodwind musical instrument, essentially a cylindrical-bore pipe sounded by a single beating reed that is clipped over a slot in a mouthpiece set in the upper end of the pipe. The lower end flares out into a bell. Modern clarinets typically are made of ebony (sometimes plastic) and have 20 or more side holes to produce different pitches; some are open, to be closed by the player's fingers, and others are covered by padded keys.
The most common size of clarinet, the B-flat soprano, has a range of about three-and-one-half octaves; the lowest note is the D (written E) below middle C. Notes above the lowest, or chalumeau, part of the range are obtained by depressing a speaker key and overblowing (increasing the speed of air blown into the instrument), which causes the instrument's air column to vibrate at a higher frequency. Being a cylindrical pipe stopped at one end, the clarinet overblows to the interval of a 12th above the fundamental pitch (unlike flutes and oboes, which overblow to the octave). Other common sizes of clarinet are the A soprano; the E-flat alto; the bass (an octave below the soprano); and the contrabass (an octave below the bass). The basset horn was a late-18th-century precursor of the alto clarinet. Music for all clarinets is written as if for a C clarinet; on a B-flat clarinet the written note C sounds as B-flat. Players can thus switch instruments without learning new fingerings. The term B-flat clarinet refers to the notation, and not to the acoustic fundamental note of the instrument.
The clarinet was invented about 1700 by the German flute maker Johann Christoph Denner as a modification of a folk reedpipe, the chalumeau. By about 1840 two complex systems of keywork had evolved: the Boehm system, used in most countries, and patented in 1844 by the French builder Auguste Buffet, who adapted the flute improvements of the German builder Theobald Boehm; and the narrower-bore, darker-sounding system developed about 1860 by the Belgian maker Eugène Albert.
To one reading an orchestral score, the clarinet is the third of the woodwind instruments from the top, following the flute and the oboe. Historically it is the fourth of them, because its invention followed that of flute, oboe and bassoon. This simple fact explains one of its most important functions in the orchestra; when it arrived, in the early part of the eighteenth century, it immediately completed the orchestral woodwind, adding a colour to the palette at the composers' disposal which filled a gap many of them had felt for a long time. Certainly one of these was the young Mozart, who wrote in a letter to his father Leopold from Mannheim: "Oh, if only we also had clarinets - you cannot imagine the splendid effect of a Symphony with flutes, oboes and clarinets." The fact that he seemed indifferent to the presence or absence of bassoons is neither here nor there - there were enough of them around to make them commonplace, and he certainly did not fail to use them with the other three in his future symphonies, whenever the full section presented itself.
The plain truth is that the clarinet is an instrument of greater flexibility than any of the other three. That is not to say it is their superior, because they all have their strong and weak points... but the clarinet has the most extensive compass of them all, almost four complete octaves.
The clarinet has the greatest dynamic range, from an inaudible ppp to a trumpet-like fff; a subler variety of tone-quality, from velvet-soft to steely-hard - and a consequent ready ability to blend with other instruments which makes it the essential 'binding' factor of the woodwind section.