Brass instruments, as their name implies, are most often made of brass - but that is not always the case. They are actually classified by the way they produce sound: the vibration of the player's lips. While the valves, slides and keys on brass instruments are used to change their overall length and therefore the pitch, fine adjustment of harmonics comes from the player's control over airflow and lip shape, known as the embouchure. This makes it possible to play instruments that lack valves or slides, such as the bugle.
Military, marching and concert bands make extensive use of brass instruments. For example, the tuba rounds out the low end of a concert symphony, while the sousaphone acts as the bass in a marching band. Some brass instruments, including the French horn, euphonium, mellophone and baritone horn, are available in separate standard and marching styles, each designed to better suit its respective playing environment. Others may be universally similar in design but with other variations between individual instruments, such as the flugelhorn, which may have three or four valves, or the trombone, which often uses an auxiliary valve to increase range or to add a trilling function.
Even brass instruments which come in relatively few configurations, such as the well-known trumpet and cornet, are frequently modified with accessories to affect their sound. A practice mute, for instance, renders the instrument near-silent, while other types of mute may simply change the tonal character. Mutes and other accessories are available from specialized manufacturers like Harmon and Jo-Ral, while some of the leading brands for brass instruments include Bach, Yamaha, Allora, Getzen and Conn.