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Re: Music Glossary - 1.64 Concert Pitch (2.12.2)

From: Stan Sanderson
Subject: Re: Music Glossary - 1.64 Concert Pitch (2.12.2)
Date: Sat, 4 Apr 2009 13:43:17 -0500

On Apr 4, 2009, at 1:42 PM, Stan Sanderson wrote:

On Apr 4, 2009, at 12:32 PM, Henning Plumeyer wrote:

Therefore, by definition, all blown > musical instruments will have a fundamental frequency of 2L.

not quite: clarinets sound an octave lower than you would expect when you regard their length. They behave like stopped organ pipes. I don't know exactly why -- it comes from their cylindrical bore. (Saxophones have a conical bore and allthough they have mouthpieces very similar to clarinets they are as long as other wind instruments.)

I think the _wavelength_ (not the frequency) of non-clarinet wind instruments is 2 times the length of the instrument.


There is an excellent tutorial on "lip reed instruments" (i.e., the brass family) at

The bore of the instrument (conical, reverse conical, or straight) influences the harmonic content of the sound produced. E.g., a clarinet and oboe have very different wave forms. I piece of standard pvc tubing attached to a clarinet mouthpiece produces an easily identifiable clarinet sound.

A piece of pvc tubing equal to the length of a trumpet can produce the expected frequency as calculated, using the length as a quarter- wave (tube closed at one end). A trumpet mouthpiece is unable to produce this tone due to the mechanics of producing the pressure "puffs" with the lips. It can be easily done with a reed.

The pressure at the lip end is either high or low. At the open end, pressure must be equal to atmospheric pressure, i.e., a node. Therefore, the pressure variation inside the tube is all multiples of 1/4 wave.

The bell of the instrument is an impedance matching device. Without the bell, most of the acoustic energy is "trapped" inside. Air inside the tube feels different to the pressure pulses than air outside. This results in the internal wave motion (pressure pulses or vibrations) which make it possible to play the instrument in the first place. The bell allows a gradual transition from the inside impedance to the external environment.

A flute is considered an open tube, even though it appears that one end is stopped. The blow hole is the other open end. Since it is open ended, the wavelength of the fundamental is twice the length of the tube.

Constructing instruments from pvc tubing can be instructive and fun!



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