© 2004 P. Missin - Details


Above is an illustration of the "free reed" used on Kratzenstein's Speaking Machine. Although it is very different from what we normally consider a free reed, it does work in the same way, ie. when subjected to a stream of air under pressure, it opens to allow the air to escape, then springs back into a closed position; it does this several times a second, chopping the airstream into short pulses, the frequency of those pulses determining the pitch of the note produced. Along with this diagram, Kratzenstein gives the following instructions (assuming my translation is accurate) for making such a reed:

Make a tube AB (fig 1) of metal or ivory, of whatever length you wish, of 9 lignes diameter (about 20mm), composed of a hollow tube BCD like the larynx, whose opening CD is narrowed a little towards C like the external glottis, but that the edge on the opposite side D is broadened so that the section of the opening CD forms a parabola EHF (fig 2), whose axis KH corresponds with the line KH (fig 1). This opening is formed by an epiglottis of metal, ivory or horn, as one wishes. However, it should be joined to the larynx at the flat side D, so that the join enjoys a kind of elasticity, due to the material of the epiglottis itself, or a spring applied to the epiglottis. Moreover, this epiglottis must fit precisely within the opening in such a way that however it is inclined, it can move up and down without friction. In the state of rest, this epiglottis must have the position KH, that is to say, inclined about half a ligne (1.13mm), closing off the tube AB. Giving the epiglottis an oscillatory movement in the direction HI, producing sound pulsations, will produce a sound similar to the human voice. The tone will depend on the degree of elasticity at the joint K, on the thickness of the epiglottis and on the degree to which one regulates the angle of inclination CH.

Over the years, many other unreedlike free reeds have been devised, including one by Professor John Robison that may predate the Kratzenstein reed. Scottish-born Robison (1739-1805) was Professor of Natural Philosophy at Edinburgh University and a prolific inventor. One of his most famous inventions was the siren, which employs a very similar method of tone generation to the free reed. Presumably around the same time, he experimented with various ways to emulate the tone of the Aeolian harp and wrote about these experiments in an article for the Encyclopedia Britannica. I have not been able to locate a copy of the original article, but a piece about the aeolina in volume VII (1829) of The Harmonicon (a Victorian music journal) quotes it thusly:

Other methods were tried which promised better: a thin round plate of metal, properly supported by a spring, was set in a round hole, made in another plate not so thin, so as just not to touch the sides. The air forced through this hole made the spring plate tremble, dancing in and out, and produced a very bold and mellow sound.

This description sounds very similar to the "reed" described in US patent # 15921, granted in 1856 to J.C. Briggs, from which the following illustration is taken:

The prolific inventor of reeds for reed organs, Merrit Gally, also came up with some similar ideas. These are from his 1886 patent (US patent 344443):

I am not at all sure that the reeds devised by Briggs and Gally ever made it past the prototype stage, nor that Robison's creation was ever used outside of his experiments.

A Brief History of Mouth Blown Free Reed Instruments
What Is A Free Reed?
Origins Of The Free Reed
Eastern Free Reed Instruments
A Selective Discography Of Asian Free Reed Instruments
Western Free Reed Instruments

Return to Main Index