The clarinet is a musical-instrument family belonging to the group known as the woodwind instruments. The clarinet has a single-reed mouthpiece, a straight cylindrical tube with an almost cylindrical bore, and a flared bell. A person who plays a clarinet is called a clarinetist (sometimes spelled clarinettist). The cylindrical bore of the clarinet is primarily responsible for the clarinet's distinctive timbre, which varies between its three main registers, known as the chalumeau, clarion, and altissimo. The tone quality of the clarinet can vary greatly with the clarinetist, music, instrument, mouthpiece, and reed. The differences in instruments and geographical isolation of clarinetists led to the development from the last part of the 18th century onwards of several different schools of playing.