Brass, or brass instruments are wind instruments that produce sound through vibrating air in a tubular resonator in sympathy with the vibration of the player’s lips. Different mechanisms, such as slides, valves, or keys are used to change effective length of tubing, while the player’s lip tension and air flow serve to select the specific harmonic produced from the available series. These days,modern brass instruments come in one of two families:
Valved brass instruments use a set of valves (usually three or four but there can be as many as seven or more) operated by the player’s fingers that introduce additional tubing, or crooks, into the instrument, changing its overall length. The valves are usually piston valves, but can be rotary valves.
Slide brass instruments use a slide to change the length of tubing. The main instruments in this category are the trombone family, though valve trombones are sometimes seen in jazz.