The horn, informally also known as the French horn, is a brass instrument made of tubing more than 20 feet long, wrapped into a coil with a flared bell. Pitch is controlled through the adjustment of lip tension in the mouthpiece and the operation of valves by the left hand, which route the air into extra tubing. Three valves control the flow of air in the single horn, which is tuned to F or less commonly B♭. The more common double horn has a fourth valve, usually operated by the thumb, which routes the air to one set of tubing tuned to F or another tuned to B♭. Triple horns with five valves are also made, tuned in F, B♭, and a descant E♭ or F. Also common are descant doubles, which typically provide B♭ and Alto F branches. This configuration provides a high-range horn while avoiding the additional complexity and weight of a triple.
A crucial element in playing the horn deals with the mouthpiece. Most of the time, the mouthpiece is placed in the exact center of the lips, but, because of differences in the formation of the lips and teeth of different players, some tend to play with the mouthpiece slightly off center. Although the exact side-to-side placement of the mouthpiece varies for most horn players, the up-and-down placement of the mouthpiece is generally two-thirds on the upper lip and one-third on the lower lip.