Page:Encyclopædia Britannica, Ninth Edition, v. 17.djvu/898

Rh 832 ORGAN Great organ reeds. The early mixtures generally included the tierce (17th, or two octaves and a third). The German practice was to unite this with a twelfth, carrying the combination 12-17 throughout the keyboard under the name of sesquialtera. It is agreed that there is no direct derivation of this use from the word, and that the name should be sexta. The combination is, however, not now usually provided. The old English sesquialtera was ordinarily simply a form of mixture, as was the furniture. The mounted cornet con sisted usually of five ranks 1 8 12 15 17. It extended from middle c upwards. The pipes were raised on a small soundboard of their own ; they were of very large scale and horn-like tone. The stop was used for re inforcing a melody. It is now obsolete. The question of the employment and composition of mixtures is of the greatest importance with respect to the good effect of the full organ proper, i.e., without reeds. With reference to the whole question of keen-toned stops it may be laid down that their free employment in the great organ does not produce a good effect unless the organ is situated in a very large space. If this is the case, properly proportioned mixtures are capable of giving to the tone of the full diapason work a character which is brilliant without being overpowering. The contrast between this class of tone and that afforded by the reeds is one of the most charming and legitimate effects within the range of the instrument. We now pass to the reeds. The 16-foot trumpet has been already alluded to, and there remain 8 trumpet and 4 clarion or octave trumpet. These are both stops of great power. The best trumpets possess also richness and smoothness of tone. Stops of this class can be used with the diapasons only, producing what may be described as a rich-toned blare of moderate strength. The more usual employment of the reeds is in connexion with the entire great organ, the whole forming the ordinary fortissimo of the instrument. Swell The second department of the English organ is the swell organ organ. The whole of the swell pipes are enclosed in a box, faced on one or more sides with a set of balanced shutters. When these are closed the tone is almost com pletely muffled. When the shutters are opened, by means of a pedal usually, the sound bursts out. In order that the use of the swell may be effective, it is necessary that the shutters should close tightly, and that there should be a sufficient volume of tone to produce an effect when they are opened. The swell is of entirely English origin ; it has been introduced in Germany to a very small extent, but more widely in France. It is usually called &quot;recitatif &quot; on the Continent. The chief characteristic of the swell is the rich and powerful volume of reed-tone of a peculiar character which it contains. But other stops are also of im portance. We consider them in order. The 16 bourdon, small scale, is very commonly used in swells. It assists in giving body to the tone. It occupies, however, a large space within the swell box ; and where the choice between it and a 16 -foot reed has to be made there can be no doubt that the reed should be preferred, as it contributes so much more to the development of the characteristic swell tone. The 16 contra fagotto and the 16 bass oboe are two alternative forms of 1 6-foot reed. The first is the more powerful of the two. Either of these stops imparts great richness to the tone of the other swell reeds, giving specially to the bass the peculiar quality which suggests great power. The 8-foot diapason work is principally valuable for the soft effects obtained from it. The diapasons are voiced less loudly than for the great organ ; and within the shutters they sound very soft indeed. The dulciana is the softest stop generally available ; and either this or some similar stop is introduced into the swell for the purpose of obtaining effects of the most extreme softness. Space within the swell box has generally to be economized. The complete bass of the open diapason or dulciana requires an 8-foot swell box, whereas even a 16-foot reed can be bent round so as to go within a smaller box if necessary. The open diapason and the dulciana are therefore often cut short at tenor c, and completed, if desired, with stopped pipes. The 4 principal and the 4 flute stops are similar to the corresponding stops in the great organ, but are somewhat lighter in tone. As in the case of the great diapasons and the 4-foot flute, it sometimes happens that the first reed combination (oboe) is not strong enough. Then the principal is sometimes put into its composition. This almost invariably spoils the effect entirely. The 2 fifteenth and mixtures are much more pleasing in the swell than in the great organ. The shutters tone them down, so that they cannot easily become offensive. Added to the reeds, they give a peculiar brilliancy to the full swell. But perhaps their most pleasing use is when all the diapason work of the swell is used alone, and as a con trast to the reeds. The usual reeds are as follows, besides the doubles already mentioned : 8 oboe, 8 cornopean, 8 trumpet, and 4 clarion (octave trumpet). The oboe (hautboy) is a conventional imitation of the orchestral instrument. It is a stop of delicate tone, and perhaps is at its best in solo passages, softly accompanied on another manual. The cornopean has a powerful horn-like tone. It is the stop which, more than any other, gives to the English swell its peculiar character. The trumpet is used in addition to the cornopean in large instruments. The clarion serves to add brightness and point to the whole. The third department is the choir organ. The 8-foot Choir work may contain 8 stopped diapason, 8 open diapason, 8 or S a11 gamba, 8 keraulophon, and 8 hohlflote. As a rule no open diapason is provided for choir organs, unless they are larger than usual ; but a small open is most useful as a means of obtaining a better balance than usual against the other manuals. The stopped diapason is gener ally made to contrast in some way with that on the great organ. The hohlflote, or its representative, is generally a lighter stop than what would be put on the great organ. The gamba is better placed in the choir organ than in the great or the swell. Such stops as the gamba and the keraulophon are frequently placed in the swell with the idea of adding to the reediness of the tone. But this is fallacious. Their tone is not strong enough to assert itself through the shutters, and their peculiar character is there fore lost. On the choir organ, on the other hand, the sort of strength required is just about what they possess, and they show to advantage. The keraulophon is a stop in vented by Gray and Davison, and has been widely adopted for many years. It has a hole made in each pipe near the top, and gives a peculiar tone very well described by its name (horn-flute). Though not very like the gamba, its tone is so far of the same type of quality that the two stops would hardly be used together. It is generally the case that similar stops of exceptional characters do not combine well, whereas stops of opposed qualities do com bine well. Thus a gamba and a keraulophon would not combine well, whereas either of them forms an excellent combination with a stopped diapason or a hohlflote. The 4 principal is sometimes very useful. A light com bination on the choir, with excess of 4-foot tone, may often be advantageously contrasted with the more full and solid tone of the great diapasons, or with other attainable effects. The 4 flute is constantly used. The 2 piccolo is frequently found on the choir organ, but is not particularly useful.