The clarinet started life as a small instrument called the 'chalumeau' (pronounced 'shall-oo-mo'). Not much is known about these instruments, but they may have evolved from recorders . The chalumeau had the same reed for producing the sound as the clarinet, but since it lacked the register key, it had a limited range of about one and a half octaves. Like a recorder, it had eight finger holes, and usually had one or two keys for extra notes.

In about 1700, a German instrument maker called Johann Christoph Denner added a register key to the chalumeau and produced the first clarinet. This instrument played well in the middle register with a loud strident tone, so it was given the name 'little trumpet' or clarinet. Early clarinets did not play well in the lower register, so chalumeaux continued to be made to play the low notes and these notes became known as the chalumeau register. As clarinets improved, the chalumeau was discontinued and forgotten.

The original Denner clarinets had two keys, but various makers added more to get extra notes. Later models had a mellower tone than the originals. The classical clarinet of Mozart's day would probably have had eight