A class of instruments having an enclosed mass of air, especially those sounded by means of the breath. The technical term for such instruments is aerophone, which, however, properly refers to all instruments in which air or wind is the primary agent of sound production, whether or not the vibrations produced are those of an enclosed column of air and whether or not the player’s breath is the wind supply. As the term wind instruments is often used, this group usually excludes keyboard instruments such as the organ, accordion, and related instruments but occasionally includes a few instruments in which a bellows has replaced the lungs (Irish union pipes, musette).
Wind instruments are generally divided into two classes, called woodwinds and brass winds. The terms woodwind and brass originated at a time when flutes, oboes, clarinets, and bassoons were all commonly made of wood, and when trumpets, horns, trombones, ophicleides, and tubas were made of brass. The names of both classes persist, though in current practice several instruments of the woodwind class are usually made of metal (flute, saxophone), and some revived early instruments related to the present-day brass group are usually made of wood (cornett, serpent).
With respect to sounding method, the brass winds are a homogeneous group. All are sounded by the vibration of the player’s lips, which are supported by a cup- or funnel-shaped “"mouthpiece. But with respect to bore (i.e., the diameter of the tube and whether the tube is more nearly cylindrical or conical) and pitch-modification method, they are more diverse. A number of methods have been devised to allow the player to produce more than one pitch. The first is the use of a more relaxed or tightened *embouchure to excite lower or higher “"harmonics in a tube of fixed length [see also Acoustics]. This allows a player of the *natu-ral trumpet or horn of the 18th century, for example, to play any of the first 13 or so pitches of the harmonic series. As one ascends through the series, more pitches become available within the space of an octave, and scale passages become possible. The second method combines playing the natural pitches with the process of altering them by means of hand positions within the bell [see Horn], The third method uses a slide to vary the length of the tube (as on the *trom-bone). The fourth uses Waives for the same purpose. A fifth uses side holes that can be covered or left open so as to vary the effective length of the tube. Although this last method has been used on lip-vibrated instruments such as the comett, ophicleide, serpent, and “"keyed bugle, no present-day brass instrument uses it.
Woodwind instruments are homogeneous in terms of pitch-changing apparatus. All have side holes that can be covered or left open so as to vary the sounding length of the tube. But they are diverse in sounding method and are thus often classed according to the method by which the air column is set into motion, whether by single reed, double reed, or no reed. These classes can be further divided.
Another basic distinction within the family of wind instruments is between whole-tube and half-tube instruments. In the former, the lowest obtainable pitch corresponds to the vibration of the column of air in its fundamental mode, i.e., the mode in which frequency is directly related to the whole length of the tube, These include brass instruments with wide bore, such as the tuba, and all woodwinds. In half-tube instruments, the fundamental is produced only with difficulty or not at all, the lowest readily obtainable pitch being the second harmonic, i.e., the one resulting from the vibration of the column of air in two halves. These include brass instruments of narrow bore, such as the trumpet, trombone, and horn.
It is obvious that much of the usual classification system for winds is arbitrary, reflecting more accurately those European types that have become commonplace than all of the combinations that are possible.
An instrument in which a column of air is the primary vibrating system. In most cases the player sets the air in motion by blowing. There are three main categories of aerophone: flutes, in which the turbulence produced by blowing across a sharp edge sets the air column in motion; lip-vibrated aerophones (primarily brass instruments), in which the air is set in motion by the vibration of the player’s lips; reedpipes (most woodwinds), in which air is set in motion by a vibrating reed.
In addition there are free aerophones, in which the vibrating air is not confined to a column (e.g., the accordion, bull-roarer, mouth organ, harmonium) or in which the column serves merely as a resonator.
Wolfgang Amadeus Mozart-Flute Concerto No 1 in G