| Since the time of the early classicism (Mannheim school) clarinet has been more represented in the symphony orchestra.
Double wind instruments are usual for classicists (2 of each: flutes, oboes, clarinets, bassoons, horns and trumpets). In the scores, it sometimes refers to the B♭ clarinets, and sometimes to A, depending on whether the composition is with flat or sharp keys. Today, if necessary, it is played in transposition (see the chapter on this.)
Romantics increase the orchestra to “triple” or “quadruple”, so that, apart from two B♭ clarinets (or A), the bass-clarinet and possibly the Es clarinet are included. The first clarinetists in the orchestra is often entrusted with expressive, technically difficult and responsible solo parts.
In the military wind band clarinets are present in larger numbers in various sizes, because there they usually have the main melody (like the violin in the symphony orchestra).
In chamber music, where the clarinet takes part, the most important is wind quintet (flute, oboe, clarinet, horn, bassoon), then the wind trio (oboe, clarinet, bassoon). There are different settings: for example, Mozart, Brahms and Reger wrote a quintet for clarinet and string quartet, and Brahms trio for clarinet, cello and piano, Beethoven has a septet for clarinet, horn, bassoon and string quartet, Schubert – octet for the same three wind instruments and string quintet. French composer Florent Schmitt has even Sextet for clarinet (one in Es, two in B♭, alto in Es, bass and contrabass clarinet).
Taken from my book