The clarinet is a single-reed instrument, the only one standard to the modern orchestra. The clarinetist blows into a mouthpiece against which a single piece of thinly carved cane vibrates with his breath. Clarinets have been built in literally all shapes and sizes down to the huge B-flat contrabass clarinet.
Clarinets have four very distinctive registers. The chalumeau is the lowest, dark and warm in tone. There is a mid-range called the "throat" register, leading to the brilliant clarion register which an early observer said "sounded from afar like a trumpet." The top range is called the extreme register.
Clarinets were developed as orchestral instruments quite recently. An inventor in Germany named Johann Christoph Denner is credited with inventing the clarinet in the early 18th century. Handel and Vivaldi were two of the first major composers to take the clarinet seriously. Mozart and Beethoven wrote beautiful chamber works for the instrument, and after his death Romantic composers like Carl Maria von Weber, Schumann, and, later, Brahms brought the clarinet to its full potential as a solo instrument.
The clarinet has been popular in jazz from the beginning, and one of the most distinctive orchestra solos for clarinet is the one that opens Gershwin's famous "jazz concerto," the Rhapsody in Blue.