A wind instrument consists of a tube containing a column of air which is set into vibration by the player blowing into (or over) a mouthpiece set into the end of the tube. The pitch is determined by the length of the tube and hence the length of the vibrating column of air.

A range of notes is obtained by:

• adjusting the effective length of the tube by one of
  • opening holes in the side of the tube, or
  • valves adding extra lengths of tubing in the middle, or
  • lengthening the tube by a sliding mechanism
• getting the column of air to vibrate at different harmonics (see harmonic series).

Wind instruments fall into one of the following categories:

• Brass instruments
• Woodwind instruments

Although brass instruments were originally made of brass and woodwind instruments have traditionally been made of wood, the material used to make the body of the instrument is not a reliable guide to its family. For example, the saxophone is made of brass but is a woodwind instrument, while the cornett and serpent, although made of wood, are in the family of brass instruments.

A more accurate way to determine whether an instrument is brass or woodwind is to examine how the player produces sound. In brass instruments, the player's lips vibrate, and that causes the air enclosed within the instrument to vibrate. In woodwind instruments, however, the player either causes a reed to vibrate which then agitates the column of air (as in a clarinet or oboe), blows against an edge (as in a recorder), or blows across an open hole (as in a flute).

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