The Hornbostel–Sachs system of musical instrument classification groups all instruments in which sound is produced through vibrating air. This can include a column of air being set in vibration (as in wind instruments) or an air-flow being interrupted by an edge (as in free-reeds). The instrument itself does not vibrate, and there are no vibrating strings or membranes.
Aerophones (4)
Free aerophones (41)
Instruments where the vibrating air is not enclosed by the instrument itself.
The air-stream meets a sharp edge, or a sharp edge is moved through the air. In either case, according to more recent views, a periodic displacement of air occurs to the alternate flanks of the edge. Examples are the swordblade or the whip.
412.1 Idiophonic interruptive aerophones or reeds - The air-stream is directed against a lamella, setting it in periodic vibration to interrupt the stream intermittently. In this group also belong reeds with a 'cover,' i.e. a tube in which the air vibrates only in a secondary sense, not producing the sound but simply adding roundness and timbre to the sound made by the reed's vibration; generally recognizable by the absence of fingerholes.
412.11 Concussion reeds - Two lamellae make a gap which closes periodically during their vibration.
412.12 Percussion reeds - A single lamella strikes against a frame.
412.121 Independent percussion reeds.
412.122 Sets of percussion reeds. - Earlier organs
412.13 Free-reed instruments feature a reed which vibrates within a closely fitting slot (there may be an attached pipe, but it should only vibrate in sympathy with the reed, and not have an effect on the pitch - instruments of this class can be distinguished from 422.3 by the lack of finger-holes).
412.14 Band reed instruments - The air hits the sharp edge of a band under tension. The acoustics of this instrument have so far not been investigated.[1]
412.2 Non-idiophonic interruptive instruments.
412.21. Rotating aerophones (the interruptive agent rotates in its own plane and does not turn on its axis)
End-struck pipe-based instruments, variations on earlier known instruments recently popularized by Blue Man Group, in forms that they refer to as Tubulum, Drumbone, etc.
The vibrating air is contained within the instrument. This group includes most of the instruments called wind instruments in the west, such as the flute or French horn, as well as many other kinds of instruments such as conch shells.
421.2 Flutes with duct or duct flutes - A narrow duct directs the air-stream against the sharp edge of a lateral orifice
421.21 Flutes with external duct - The duct is outside the wall of the flute; this group includes flutes with the duct chambered in the wall under a ring-like sleeve and other similar arrangements.
421.211.2 Partly stopped flutes with external duct.
421.211.3 Stopped flutes with external duct.
421.212 Sets of flute with external duct.
421.22 Flutes with internal duct - The duct is inside the tube. This group includes flutes with the duct formed by an internal baffle (natural node, bock of resin) and an exterior tied-on cover (cane, wood, hide).
422.3 Reedpipes with free reeds - The reed vibrates through [at] a closely fitted frame. There must be fingerholes, otherwise the instrument belongs to the free reeds 412.13.
422.31 Single pipes with free reed.
422.32 Double pipes with free reeds.
Trumpets (423)
The player's vibrating lips set the air in motion.
423.1 Natural trumpets - There are no means of changing the pitch apart from the player's lips.