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 finger-holes.

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).

412.131 Individual free reeds.

412.131 Individual free reeds – Bawu, Party Horn, Pitch-Pipes.
412.132 Sets of free reeds.

Party horn
Pitch pipe
412.132 Sets of free reeds.

Accordica (mouth organ)
Accordina (instrument)
Accordolin (mouth organ)
Reed organ
Vibrandoneon (instrument)

412.2 Non-idiophonic interruptive instruments.

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.

412.21 Rotating aerophones the interruptive agent rotates in its own plane and does not turn on its axis.

412.22 Siren, Bull-Roarer & Corrugaphone – Whirling aerophones, the interruptive agent turns on its axis.

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