The clarinet was a relatively late developer compared to many orchestral instruments. Reed instruments had been used throughout history across the world, in Ancient Greece, Egypt, the Middle East, and from the Middle Ages they were found in Europe. The actual clarinet did not appear until the late 1600s, when Johann Christopher Denner from Germany adapted a baroque single reed instrument called the chalumeau.
The chalumeau was used widely in Europe, but only occasionally in orchestras. Similar to a recorder it had seven holes including a thumb hole. It had two keys, to play the two highest notes, but its range of one and a half octaves was rather limiting. Christopher Denner, with the help of his son Jacob, therefore converted one of the existing keys to make it the register key.
When held down, the register key allowed players to produce notes a 12th higher in pitch than normal. This increased the instrument’s range hugely. The clarinet produced a loud, shrill sound which resulted in the name being derived from the Italian word ‘clarino’ which means ‘little trumpet’.
At this point the instrument could be played with the clarinettist’s hands either way around (it didn’t matter if the left or right hand was on top). However, by the classical period it had been developed to five keys, so this unusual flexibility disappeared.
The clarinet was still not a standard instrument of the orchestra, but Mozart loved it and so included it in his orchestral compositions, as well as writing a lot of solo repertoire for it. It is said that he considered it the instrument closest in quality to the human voice.
By the time Beethoven was composing it was usual to have clarinets in an orchestra, and it was during his life that a great leap was made in the design of the instrument. The pads under the keys were originally made of felt, and were not very airtight. In 1812 a Russian clarinettist and composer, Iwan Müller, invented pads covered in leather or fish bladder (modern instruments have cork or synthetic pads). The fact that the keys were now airtight meant the instrument could have a larger number of them without the sound being affected. Müller’s clarinet design had seven finger holes and a whopping thirteen keys. This removed the need for different instruments for different key signatures.
Another change came in around 1820, when the reed moved from being at the top of the mouthpiece to being at the bottom. The Germans lead the way with this, and France and England followed.
The last major change was the result of clarinettist Hyacinthe Klosé and instrument technician August Buffet in 1839. Klosé was inspired by the flute keywork design by Theobold Boehm, and enlisted the help of Buffet to construct a new clarinet.
They rearranged the keys and finger holes on the instrument, and credited Boehm’s influence by naming the design after him. This new clarinet took a while to catch on, as it required players to learn a whole new fingering system, but today the Boehm system is used everywhere in the world except Germany and Austria.