An aerophone is any
musical instrumentwhich produces soundprimarily by causing a body of air to vibrate, without the use of strings or membranes, and without the vibration of the instrument itself adding considerably to the sound. It is one of the five main classes (class 4) of instruments in the original Hornbostel-Sachsscheme of musical instrument classification.
Hornbostel-Sachs divides aerophones by whether vibrating air is contained in the instrument itself or not.
The first class (41) includes instruments where the vibrating air is "not" contained by the instrument itself, such as the bullroarer. Such instruments are called "free aerophones". This class includes
free reedinstruments, such as the harmonica, but also many instruments unlikely to be called wind instruments at all by most people, such as sirens and whips.
The second class (42) includes instruments where the vibrating air "is" contained by the instrument. This class includes almost all the instruments generally called
wind instruments in the west, such as the flute, sheng, the oboeand the trombone.
Additionally, very loud sounds can be made by explosions directed into, or being detonated inside of resonant cavities. Instruments such as the calliope (and steam whistle), as well as the
pyrophonemight thus be considered as class 42 instruments, despite the fact that the "wind" or "air" may be steam or an air-fuel mixture.
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