The term double clarinet refers to any of several woodwind instruments consisting of two parallel pipes made of cane, bird bone, or metal, played simultaneously, with a single reed for each. Commonly, there are five or six tone holes in each pipe, or holes in only one pipe while the other acts as a drone, and the reeds are either cut from the body of the instrument or created by inserting smaller, slit tubes into the ends of the pipes. The player typically uses circular breathing.
The double clarinet is not a clarinet in the modern western sense of the term, since it lacks a register key; in this regard it is more closely related to the chalumeau.