1911 Encyclopædia Britannica/Mouthpiece

Britannica Mouthpiece Organ Flue-Pipe.png

From V. Mahillon, Éléments d'acoustique, by permission of C. Mahillon.

Fig. 1. — Diagram of a flue-pipe.

MOUTHPIECE (Fr. embouchure; Ger. Mundstück; Ital. bocchino), in music, that part of a wind instrument into which the performer directs his breath in order to induce the regular series of vibrations to which musical sounds are due. The mouthpiece is either taken into the mouth or held to the lips; by an extension of the meaning of the word, mouthpiece is also applied to the corresponding part of an organ-pipe through which the compressed wind is blown, and containing the sharp edge known as “lip,” or the reed necessary for the production of sound. The quality of a musical tone is due primarily to the form or method of vibration by means of which sound-waves of a distinctive character are generated, each consisting of a pulse or half-wave of compression and of a pulse of rarefaction; the variety in the quality of tone, or “timbre,” obtainable in various wind instruments is in a great measure due to the form and construction of the mouthpiece, taken in combination with the form of the column of air within the tube and consequently of the bore of the latter. The principal functions of the mouthpiece are (1) to facilitate the production of the natural harmonic scale of the instrument; (2) to assist in correcting errors in pitch as the ear directs; (3) to enable the performer to obtain the dynamic variations whereby he translates his emotional interpretation of the music into sound. Mouthpieces, therefore, serve as a means of classifying wind instruments. They fall into the following divisions: —

1. The syrinx or pan-pipe mouthpiece consists merely of the open end of the tube across (not into) which the player directs his breath in a current which impinges obliquely against the sharp edge of the pipe, producing the. series of shocks or pulses required in the air stream from his lips; this in turn, when in a state of vibration, serves to generate the sound-waves within the pipe. This principle was embodied in the nay, or long oblique flute of the ancient Egyptians, which was probably the first mouthpiece discovered and put into practical use by prehistoric man. A modification of this principle has been applied to the transverse flute (q.v.), in which the air stream or exciting current is directed across a lateral hole in the head joint of the instrument.

2. The whistle mouthpiece is based on that of the flute with this modification, that the air current, instead of being compressed by the lips of the performer and then directed through ambient air to break against the sharp edge of the lateral hole, is compressed mechanically in passing through a narrow channel so constructed within the mouthpiece that the stream of air impinges with force against the sharp edge of a lip cut into the pipe below the channel. The principle of the whistle mouthpiece has been applied with slight modifications to a variety of instruments such as the recorder (q.v.) family in England (Fr. flûte à bec, flûte douce, flûte anglaise; Ger. Schnabelflöte, Plockflöte; Ital. flauto dolce, in which the channel assumes the form of a beak, the flageolet (q.v.), the penny whistle, &c. All these whistle or fipple pipes have at all times enjoyed great popularity owing to the ease with which they can be played.[1]

The flute or flue-work of an organ is the result of the adaptation of the same principle to both open and stopped pipes (fig. 1). Compressed air is fed in at an even pressure through the foot AB, and passing through the slit or channel EC, impinges with force against the lip D, producing the requisite series of pulsations in the pipe FF. By this elimination of the human element in the organ, all possibility of communicating the emotion of the performer becomes impossible. With a rigid mouthpiece any increase in wind pressure would affect the pitch, causing the note to become unsteady or to jump to the harmonics; the result could in no case be a crescendo.

3. Reed Mouthpieces. — There are three kinds of reed mouthpieces: the double, the single or beating, and the free reed. The function of the reed, a term originally applied to part of a stalk of the Arundo donax or sativa, but now extended to any vibrating tongue of wood or metal, is to break up an exciting current of air, otherwise flowing in an uninterrupted even stream, into regular beats or pulses, corresponding with the beats or vibrations of the reed. Reeds proper or wooden vibrators, being flexible, are compelled to vibrate synchronously with the column of air within the tube and to accommodate their frequency of vibration to the length of the tube as it varies according to the lateral holes which remain open.[2]

A. The double reed is the most primitive and probably the oldest of the reed mouthpieces; it was used by the ancient Egyptians.[3] A straw flattened at one end and inserted into a pipe having at the mouthpiece end the same diameter as the straw contains all the rudimentary features of the double-reed mouthpiece common to the members of the oboe family, i.e. cor anglais, bassoon, contra-fagotto, to the sarrusophone, and to the chaunter of the bagpipe. The earliest Greek aulos (q.v.) was probably played by means of a double reed, since the mouthpiece was known as ζεῦγος, signifying a pair of like things. The oboe reed (fig. 2) is made from two pieces of reed stalk, flattened and thinned at the end and bound together with waxed thread, thus forming a tube with a constriction in the middle, above which the section is oval and below circular.

Britannica Mouthpiece Double Reed.png
Rudall Carte & Co.
Fig. 2. — Oboe double-reed mouthpiece.

A double-reed mouthpiece may be enclosed in an air-chamber or reservoir, as in the 16th-century cromorne (q.v.), in the chaunter of the bagpipe (q.v.), in the reeds of organ-pipes and in certain instruments popular in France during the 17th century known as “hautbois de Poitou.” In all of these the air-chamber is supplied with compressed air by the mouth of the performer, whose lips do not come into contact with the reed, a method which makes the production of harmonics impossible, and thus restricts the natural scale. As soon as the practice of over-blowing, i.e. the production of harmonics by increased pressure of breath accompanied by a proportional tension of the lips, became known, the air-chamber of the oboe was discarded and the reed taken directly into the mouth. It is certain that the ancient Greeks obtained the full compass of the aulos by overblowing, since the process by which a modern performer on the oboe or clarinet obtains the harmonics is described by Aristotle[4] and others.[5]

The vibrating length of the reed is controlled by taking the latter more or less deeply into the mouth and by varying the pressure of the lips upon it; the shorter the free end the higher the pitch of the note or harmonic obtained. The action of the lips on the reed is imitated to some extent in reed organ-pipes by means of a tuning-wire, with the difference that, the lips being mobile, different notes can be obtained from the same pipe, whereas in the organ each reed is adapted to its own pipe and gives one note only.

Britannica Mouthpiece Single Reed.png
Fig. 3. — Clarinet Mouthpiece.

a, The mouthpiece, the position of the bore inside being indicated by dotted lines.
b, The single- or beating-reed.

B. The beating- or single-reed mouthpiece, also known as the clarinet mouthpiece, is likewise of great antiquity; the principle is the same as that of the modern Egyptian arghoul (q.v.), which has been traced once at least in the hieroglyphics and in a fresco from the tombs at Saqqara.[6] The mouthpiece of the arghoul is the primitive form of beating-reed known popularly in rural districts as a “squeaker.” A lateral slit is made in a piece of reed and a little tongue is detached by slitting the reed back from the slit towards a knot. The breath causes the reed-tongue to close and open the aperture at regular intervals, and the exciting agent here acts by means of a series of concussions. The metal vibrator known as the beating-reed of organ reed-pipes is similarly con- structed, except that the tongue is a separate piece of metal fixed by means of nuts over an aperture, the vibrating length being regu- lated by means of a tuning-wire (see Free Reed Vibrator). The clarinet mouthpiece (fig. 3) has the appearance of a beak with the point bevelled and thinned at the edge to correspond with the end of the reed, shaped like a spatula. The underpart of the mouthpiece is flattened in order to form a table for the support of the reed, which is adjusted thereon with great nicety by means of a ligature or metal band fastened by screws. A longitudinal aperture 1 in. long and ½ in. wide, communicating with the bore, is cut in the table and covered by the reed, so that the only opening is at the point, where for the distance of ⅓ to ¼ in. the reed is thinned and the table curves backwards, leaving a gap of about 1 mm. between itself and the reed-tongue, (for the B♭ clarinet). The curve of the table and the dimensions of the gap are therefore of considerable importance, The reed is set in vibration by the breath of the performer, and being flexible it beats against the table, alternately opening and closing the gap, and producing, as already mentioned above, a series of concussions in harmony with the vibrations of the air-column within the tube, according to the length determined by the opening of the lateral holes and keys.

C. The free-reed, illustrated under Free Reed Vibrator, is similar in construction to the beating-reed, but the metal vibrator is cut slightly smaller than the aperture, through which it passes freely, alternately opening and closing it without concussion and with complete elasticity. The main difference in practice between these two outwardly similar reeds is a very important one. The reed being free remains uncontrolled, and increased pressure of wind therefore produces not an harmonic overtone but a crescendo. The principal use of the free-reed is in the harmonium (q.v.) and in the reed-work of organs on the continent of Europe. In English organs the beating-reed is almost universal. The free-reed is further used in the Chinese cheng (q.v.), through which it became known in Europe in the 18th century, and in the accordion, concertina and mouth-organ, under which headings its acoustic properties are more fully discussed.

4. Cup-Mouthpieces. — Brass wind instruments are played by means of cup or funnel-shaped mouthpieces, generally made of silver. The principal feature of the cup is the shape of the aperture in the bottom, where it communicates with the bore of the tube (known as the “gruin” or “throat”), and its distance from the rim. The shallower the cup the more suitable it is for producing the higher harmonics. The lips of the performer rest lightly but firmly against the rim of the mouthpiece, vibrating like double reeds from the force of the breath and communicating these vibrations in the form of pulses to the breath as it issues from them in a stream. This stream or exciting current passes into the cup ready to generate sound-waves in the air column contained within the main tube. If, as in the trumpet and in a lesser degree in the trombone, the curve of the bottom of the cup terminates at the hole in an abrupt angle, the quality of the tone developed is brilliant and blaring, being broken up by the sharp edge of the throat. In the horn, which has a funnel-shaped mouthpiece, the timbre is in complete contrast when the instrument is properly played,[7] being elastic, sonorous and very mellow, qualities which may be attributed to the absence of angle or bottom to the cup, the sides gradually sloping and converging insensibly into the bore of the tube. (K. S.)

  1. See Rev. F. W. Galpin, “The Whistles and Reed Instruments of the American Indians of the North-West Coast,” Proc. Musical Assoc. (1903-1904), p. 115, with illustrations.
  2. See Victor Mahillon, Éléments d'acoustique musicale (Paris, 1873), pp. 167 and 83.
  3. A case excavated in Egypt was found to contain two pipes, and in addition five pieces of reed without bore or holes, and three pieces of straw suitable for making double-reed mouthpieces. See Victor Loret, “Les Flûtes égyptiennes antiques,” Journal asiatique (Paris, 1889), [8], xiv. pp. 119, 200, 201 (note), 207, 211 and 217.
  4. See De audib. p. 804a.
  5. Porphyrius (ed. Wallis), pp. 249 and 252.
  6. See Victor Loret, L'Egypte au temps des Pharaons (Paris, 1889), illustrated on pp. 139 and 143. The author gives no information as to this fresco except that it is in the Musée Guimet; it is probably identical with the second of the mural paintings described on p. 190 of the Petit guide illustré du Musée Guimet (Paris, 1890).
  7. The horn may be so played, by forcing the breath in a certain manner, that its timbre approximates to that of the trumpet.