three-rank mixture may consist of the following (the numbers signify
intervals, reckoned along the scale)
C — c (tenor) 15 — 19 — 22
c# to top 8 — 12 — 15.
For a somewhat larger full mixture this may be modified as follows —
C—c' (middle) 15—19—22
c'S to top I — 8—12—15.
A sharp mixture suitable for a large instrument may be as follows Five Ranks.
C — c' 15 — 19 — 22 — 26 — 29
c'Uf—fii 8-12-15-19-22
g"—c" I— 8— 12— 15— 19
c'" to top I — 5 — 8— 12— 15.
The last two compositions are given by Hopkins in his great treatise on the organ.
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. The combination is not now usually provided. The old English sesquialtera was ordinarily s'mply a form of mixture, as was the furniture. The mounted cornet consisted usually of five ranks
I— 8— 12— 15— 17.
It extended from middle c upwards. The pipes were raised on a small soundboard of their own. The stop was used for giving out 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 arc 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 i6-ft. 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.
The second department of the English organ is the swell 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 completely 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 " recitatif " 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 importance. 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 i6-ft. 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 is the usual name of this stop. It imparts great richness to the tone of the other swell reeds.
The 8-ft. diapason work is principally valuable for the soft effects obtained from it. The diapasons are voiced less loudly than for the great organ; and with the shutters closed they sound very soft. 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-ft. swell box, whereas even a l6-ft. 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, hut are somewhat lighter in tone.
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 contrast to the reeds.
Great
organ
Choir
organ.
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 vox humana is also frequently placed on the swell.
The third department is the choir organ. The 8-ft. work may contain 8 stopped diapason, 8 open diapason, 8 gamba, 8 keraulophon and 8 hohlflcite.
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 generally 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 therefore 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 invented 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 combine 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 combination on the choir, with excess of 4-ft. 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.
In organs which have no solo manual there is usually a clarinet (cremona, cromorne or krummhorn, in old organs sometimes corno di bassetto) on the choir, and often an orchestral oboe (real imitation of the instrument). These are reed-stops. The dulciana and another soft stop, the salicional, salcional or salicet (of similar strength, but slightly more pungent quality), are often placed on the choir. They are, however, hardly strong enough to be of much use there, and in the swell they are useful for effects of extreme softness. In very large instruments a fifteenth and a mixture are sometimes placed on the choir, which in this case has a complete series of diapason work. If the fifteenth and the mixtures are light enough the result is a sort of imitation of the tone of the old English organ. It also forms a useful echo to the great organ, i.e. a passage played on the great may be repeated on the similar but fainter tone of the choir with the effect of an echo. In instruments of the largest size the choir is sometimes provided with a very small bourdon of i6-ft. tone, which helps to give to the tone the character of that of a small full organ without reeds.
The solo organ is comparatively modern, at all events in its present usual form. A fourth manual was not unknown in old German organs; but the contents of all four resembled each other in a general sort of way, and there was nothing like the English swell or the modern solo. The solo appears to have arisen with Cavaill6-Coll in France, and Hill in England, as a vehicle for the powerful reed-stops on heavy wind introduced by these builders. Thus the French term for the solo is "clavier des bombard es"; and in the earlier English solos the " tuba mirabilis " was usually prominent. A solo organ may suitably contain any of the following stops: 8 tromba (a powerful reed on heavy wind), 8 harmonic flute (powerful tone and heavy wind), 8 clarinet and 8 orchestral oboe (real imitations of the instruments) and 8 vox humana (conventional imitation of the human voice). The last three stops are reeds. They may be with advantage enclosed in a swell box, having a separate pedal. In very large instruments a complete series of both diapason and reed stops is occasionally placed on the solo. But there does not seem to be much advantage in this arrangement.
We now come to the pedal. This forms the general bass to the whole organ. Thirty-two foot stops only occur in the largest instruments; they are as follows: 32 open diapason (wood or metal), 32-ft. tone bourdon and 32 contra trombone, posaune, bombarde, sackbut (reed). The 32-ft. open diapason, whether wood or metal, is usually made of large scale, and produces true musical notes throughout. Its musical effect in the lower part of its range is, however, questionable, so far as this depends on the possibility of recognizing the pitch of the notes. It adds great richness to the general effect, particularly in large spaces. The 32-ft. tone bourdon is not usually a successful stop.
Solo
organ.
Pedal
organ.
