The Oehler system is a system for clarinet

Clarinet

The clarinet is a musical instrument of woodwind type. The name derives from adding the suffix -et to the Italian word clarino , as the first clarinets had a strident tone similar to that of a trumpet. The instrument has an approximately cylindrical bore, and uses a single reed...

 keys developed by Oskar Oehler. Based on the Müller system

Ivan Mueller

Ivan Mueller was a clarinetist, composer and inventor who at the beginning of the 19th century was responsible for a major step forward in the development of the clarinet, the air-tight pad....

 clarinet, the system adds tone holes to correct intonation and acoustic deficiencies, notably of the forked notes (B♭ and F). The system has more keys than the Boehm system, up to 27 in the Voll-Oehler system (full Oehler system). It also has a narrower bore and a longer, narrower mouthpiece leading to a slightly different sound. It is used mostly in Germany

Germany

Germany , officially the Federal Republic of Germany , is a federal parliamentary republic in Europe. The country consists of 16 states while the capital and largest city is Berlin. Germany covers an area of 357,021 km2 and has a largely temperate seasonal climate...

 and Austria

Austria

Austria , officially the Republic of Austria , is a landlocked country of roughly 8.4 million people in Central Europe. It is bordered by the Czech Republic and Germany to the north, Slovakia and Hungary to the east, Slovenia and Italy to the south, and Switzerland and Liechtenstein to the...

. Major developments include the patent C♯, low E-F correction, fork-F/B♭ correction and fork B♭ correction. Fingering charts can be found for example in this reference.

Oehler system clarinet makers

Oskar Oehler had three students: F. Arthur Uebel, Ludwig Warschewski and K.F. Todt. Uebel and Todt are legendary clarinet makers in Germany, while Warschewski moved to Stockholm

Stockholm

Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...

 and became the solo clarinetist of Stockholm Philharmonic. Warschewski bought semi-finished Uebel clarinets and worked on the bore and mechanics. His clarinets are used by famous clarinetists like Dieter Klöcker

Dieter Klöcker

Dieter Klöcker was a German clarinetist known for rediscovering many forgotten masters of the 18th century...

. Uebel clarinets were used by Karl Leister

Karl Leister

Karl Leister is a classical clarinet player from Wilhelmshaven, Germany. At a very young age, he learned to play the clarinet from his father, also a clarinetist, and later studied at the Hochschule fur Musik in Berlin...

 when he first joined the Berlin Philharmonic; later he changed to Wurlitzer. Wurlitzer clarinets made before the 1970s sounded very much like the Uebel clarinets while the bigger bore gave them better intonation. After the 1970s, Wurlitzer made some modifications to their design. Wurlitzer clarinets are now used in the great majority of German orchestras. They are very expensive, but some Wurlitzer apprentices are producing similar clarinets for less.