Page:EB1911 - Volume 12.djvu/984

Rh their keys. Dawes’s “melody attachment” is to give prominence to an air or treble part by shutting off in certain registers all notes below it. This notion has been adapted by inversion to a “pedal substitute” to strengthen the lowest bass notes. The “tremolo” affects the wind in the vicinity of the reeds by means of small bellows which increase the velocity of the pulsation according to pressure; and the “sourdine” diminishes the supply of wind by controlling its admission to the reeds.

The American Organ acts by wind exhaustion. A vacuum is practically created in the air-chamber by the exhausting power of the footboards, and a current of air thus drawn downwards passes through any reeds that are left open, setting them in vibration. This instrument has therefore exhaust instead of force bellows. Valves in the board above the air-chamber give communication to reeds (fig. 2) made more slender than those of the harmonium and more or less bent, while the frames in which they are fixed are also differently shaped, being hollowed rather in spoon fashion. The channels, the resonators above the reeds, are not varied in size or shape as in the harmonium; they exactly correspond with the reeds, and are collectively known as the “tube-board.” The swell “fortes” are in front of the openings of these tubes, rails that open or close by the action of the knees upon what may be called knee pedals. The American organ has a softer tone than the harmonium; this is sometimes aided by the use of extra resonators, termed pipes or qualifying tubes, as, for instance, in Clough & Warren’s (of Detroit, Michigan, U.S.). The blowing being also easier, ladies find it much less fatiguing. The expression stop can have little power in the American organ, and is generally absent; the “automatic swell” in the instruments of Mason & Hamlin (of Boston, U.S.) is a contrivance that comes the nearest to it, though far inferior. By it a swell shutter or rail is kept in constant movement, proportioned to the force of the air-current. Another very clever improvement introduced by these makers, who were the originators of the instrument itself, is the “vox humana,” a smaller rail or fan, made to revolve rapidly by wind pressure; its rotation, disturbing the air near the reeds, causes interferences of vibration that produce a tremulous effect, not unlike the beatings heard from combined voices, whence the name. The arrangement of reed compartments in American organs does not essentially differ from that of harmoniums; but there are often two keyboards, and then the solo and combination stops are found on the upper manual. The diapason treble register is known as “melodia”; different makers occasionally vary the use of fancy names for other stops. The “sub-bass,” however, an octave of 16 ft. pitch and always apart from the other reeds, is used with great advantage for pedal effects on the manual, the compass of American organs being usually down to F (FF, 5 octaves). In large instruments there are sometimes foot pedals as in an organ, with their own reed boxes of 8 and 16 ft. the lowest note being then CC. Blowing for pedal instruments has to be done by hand, a lever being attached for that purpose. The “celeste” stop is managed as in the harmonium, by rows of reeds tuned not quite in unison, or by a shade valve that alters the air-current and flattens one row of reeds thereby.

Harmoniums and American organs are the result of many experiments in the application of free reeds to keyboard instruments. The principle of the free reed became widely known in Europe through the introduction of the Chinese cheng during the second half of the 18th century, and culminated in the invention of the harmonium and kindred instruments. The first step in the invention of the harmonium is due to Professor Christian Gottlieb Kratzenstein of Copenhagen, who had had the opportunity of examining a cheng sent to his native city and of testing its merits. In 1779 the Academy of Science of St Petersburg had offered a prize for an essay on the formation of the vowel sounds on an instrument similar to the “vox humana” in the organ, which should be capable of reproducing these sounds faithfully. Kratzenstein made as a demonstration of his invention a small pneumatic organ fitted with free reeds, and presented it to the Academy of St Petersburg. His essay was crowned and was republished with diagrams in Paris in   1782. Meanwhile, in 1780, a countryman of Kratzenstein’s, an organ-builder named Kirsnick, established in St Petersburg, adapted these reed pipes to some of his organs and to an instrument of his invention called organochordium, an organ combined with piano. When Abt Vogler visited St Petersburg in 1788, he was so delighted with these reeds that in 1790 he induced Rackwitz, an assistant of Kirsnick’s, to come to him and adapt some to an organ he was having built in Rotterdam. Three years later Abt Vogler’s orchestrion, a chamber organ containing some 900 pipes, was completed, and, according to Rackwitz, was fitted with free-reed pipes. Vogler himself, however, does not mention the free reed when describing this wonderful instrument and his system of “simplification” for church organs. To Abt Vogler, who travelled all over Germany, Scandinavia and the Netherlands, exhibiting his skill on his orchestrion and reconstructing many organs, is due the credit of making Kratzenstein’s invention known and inducing the musical world to appreciate the capabilities of the free reed. The introduction of free-reed stops into the organ, however, took a secondary place in his scheme for reform. Friedrich Kaufmann of Dresden states that Vogler told him he had imparted to J. N. Mälzel of Vienna particulars as to the construction of free-reed pipes, and that the latter used them in his panharmonicon, which he exhibited during his stay in Paris from 1805 to 1807. Kaufmann suggests that it was through him that G. J. Grenié obtained the knowledge which led to his experiments with free reeds in organs. It is more likely that Grenié had read Kratzenstein’s essay and had experimented independently with free reeds. In 1812 his first orgue expressif was finished. It was a small organ with one register of free reeds—the expression stop, in fact, added to the pipe organ and having a separate wind-chest and bellows. It would seem from his description of the orchestrion in Data zur Akustik that Vogler knew of no such device. He used the swell shutter borrowed from England and a threefold screen of canvas covered with a blanket arranged outside the instrument, neither of which is capable of increasing the volume of sound from the organ, or at least only after having first damped the sound to a pianissimo. Vogler explains minutely the apparatus used to conceal the working of the screen from the eyes of the public. The credit of discovering in the free reed the capability of dynamic expression was undoubtedly due to Grenié, although Abt Vogler claims to have used compression in 1796, and Kaufmann in his choraulodion in 1816. A larger orgue expressif was begun by Grenié for the Conservatoire of Paris in 1812, the construction of which was interrupted and then continued in 1816. Descriptions of Grenié’s instrument have been published in French and German. The organ of the Conservatoire had a pedal free-reed stop of 16 ft., with vibrators 0.240 m. long, 0.035 m. wide, and 0.003 m. thick. Two compressors, one for the treble and the other for the bass, worked by treadles, enabled the performer to regulate the pressure of wind on the reeds and therefore to obtain the gradations of forte and piano which gained for his instrument the name of orgue expressif. Grenié’s instrument was a pipe organ, the pipes terminating in a cone with a hemispherical cap in the top of which was a small hole. There were eight registers including the pedal, and the positive on the first keyboard had reed stops furnished with