This Section
next Fourth Method.
In the fourth method a flexible reed is used. This may be (a)
a single-reed, or (b) a double-reed.
(a) If it is a single-reed, it may be either what is known as a " single-beating-reed " or a " free-single-reed." All orchestral single-reed instruments are blown with a beating-reed. This is so arranged that, when set in motion by the player's breath, it beats against the" table " at the upper end of the pipe, rapidly opening and closing the aperture.
The families of Clarinets and Saxophones belong to this subdivision, and the subdivision is generally known as one of Pipes with reed-mouthpieces. In the case of the "reed-pipes" of the Organ the action is very much the same as that described above, but the "reed" itself is simply a strip of flexible metal.
The "free-single-reed" is not used in any orchestral instrument. In fact, the only instrument in which it has been put to practical use is the Harmonium. In this instrument the metal " reeds " are " set" in a series of apertures into which they just fit. Sufficient freedom is, however, left for them to vibrate to and fro. The amount of " play " is so adjusted that, while the reed can actually vibrate, it practically closes and opens the aperture at each vibration. It is thus able to communicate the vibratory motion to the enclosed air-space.
In the ancient Regal—a small " Positive " as opposed to a " Portative" Organ—the stops were originally reed-stops. The reeds employed were much like those of the Clarinet and Saxophone, "single-beating-reeds." However, like those of the Organ, they were made of metal, not of cane. Scientifically they were quite distinct from the " free-single-reeds " of the Harmonium.
(b) In the case of the double-reed, two flexible pieces of "cane" are bound vis-a-vis in this shape (). The aperture between the upper-ends of the two " canes" is extremely small. The player takes the double-reed between his lips, and, by the pressure of his lips and breath, forces it to vibrate. At each vibration, the narrow aperture between the two "canes" is alternately opened and closed. This, the second section of the subdivision, Pipes with reed-mouthpieces, is represented by the ancient Schalmeys and Pommers and the modern Oboe and Bassoon families.
The two kinds of Wood-Wind instrument with which we have been dealing, viz. those played with single-beating-reeds and those played with double-reeds, may be conveniently distinguished according to the bore of their pipes, as
(a) Cylindrical pipes...(The single-beating-reed Clarinet group).
(b) Conical pipes...... ..(The double-reed Oboe and Bassoon group).
A special Percussion apparatus is also used in the Harmonium to remedy its slow-ness of speech. At the moment that the air-stream is directed on to the reed a tiny hammer taps it into action.
For the sake of completeness the Jews' Harp must be mentioned. In this instrument the air-vibrations are set up by means of a single tongue of flexible metal. The air-space inside the mouth is the resonating-cavity. The shape and size of this cavity are altered by the muscles of the cheeks so as to reinforce the various Harmonics already present in the vibrating metal-tongue. A certain additional prominence can thus be given to any desired note in the Harmonic Series.