Bell (wind instrument)

A wind instrument is a musical instrument that contains some type of resonator (usually a tube), in which a column of air is set into vibration by the player blowing into (or over) a mouthpiece set at or near the end of the resonator. The pitch of the vibration is determined by the length of the tube and by manual modifications of the effective length of the vibrating column of air. In the case of some wind instruments, sound is produced by blowing through a reed; others require buzzing into a metal mouthpiece.

Almost all wind instruments use the last method, often in combination with one of the others, to extend their register.

Wind instruments are typically grouped into two families:

Although brass instruments were originally made of brass and woodwind instruments have traditionally been made of wood, the material used to make the body of the instrument is not always a reliable guide to its family type. A more accurate way to determine whether an instrument is brass or woodwind is to examine how the player produces sound.

For example, the saxophone is typically made of brass, but is classified as a woodwind instrument because it produces sound with a vibrating reed.

On the other hand, the didgeridoo, the wooden cornett (not to be confused with the cornet, which is made of brass) and the serpent are all made of wood (or plastic tubing, in the case of modern serpents), and the olifant made from ivory, but all of them belong to the family of brass instruments because the vibrating is done by the player's lips.

In the Hornbostel-Sachs scheme of musical instrument classification, wind instruments are classed as aerophones.

Sound production in all wind instruments depends on the entry of air into a flow-control valve attached to a resonant chamber (resonator). The resonator is typically a long cylindrical or conical tube, open at the far end. A pulse of high pressure from the valve will travel down the tube at the speed of sound. It will be reflected from the open end as a return pulse of low pressure. Under suitable conditions, the valve will reflect the pulse back, with increased energy, until a standing wave forms in the tube.

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