The Recent Revolution in Organ Building Part 9

Mr. Hope-Jones informs the writer that he has just invented an electric action which strikes a blow accurately proportioned to the force employed in depressing the key, thus obtaining expression from the fingers as in the pianoforte. He will apply this to the percussion stops in organs he may build in the future.

When skilfully employed many of these percussion stops blend so perfectly with the flue and reed pipes that they become an important integral part of the instrument--not merely a collection of fancy stops for occasional use.

THE DIAPHONE.

The invention of the Diaphone by Hope-Jones in 1894 will some day be regarded as the most important step in advance hitherto achieved in the art of organ building. The existence of patents at present prevents general adoption of the invention and limits it to the instruments made by one particular builder. In addition to this the Diaphone takes so many forms and covers so large a field that time must necessarily pa.s.s before its full possibilities are realized.

Enough was, however, done by Hope-Jones in connection with the organs he built in England a dozen or eighteen years ago to leave the experimental stage and prove the invention to be of the greatest practical importance to the future of organ building. The author's opinion that before long every new large organ will be built upon the Diaphone as a foundation, is shared by all who have had opportunity to judge. By no other means known to-day can anything approaching such grand and dignified Diapason tone be produced. Were twenty large Diapasons added to the instrument in Ocean Grove, N. J., or to that in the Baptist Temple, Philadelphia, and were the Diaphone removed, the instrument would suffer most seriously. In the Pedal department no reed or flue pipe can begin to compare with a Diaphone, either in attack or in volume of tone.

In Figure 23 we give a sectional view of the first large Diaphone made, namely that constructed for the Hope-Jones organ in Worcester Cathedral, Eng., 1896.

[Ill.u.s.tration: Fig. 23. Diaphone in Worcester Cathedral, Eng.]

M is a pneumatic motor or bellows to which is attached a rod bearing the compound and spring valve V, V|1|, working against the spring S.

On the admission of wind (under pressure) to the box A, the motor M is caused to collapse, and thereby to open the valves V, V|1|. Wind then rushes into the chamber B, and entering the interior of motor M through the pa.s.sage C, equalizes the pressure in the motor. The action of the springs now serves to close the valves V, V|1|, and to open out the motor M, whereupon the process is repeated.

[Ill.u.s.tration: Fig. 24. Diaphone in Aberdeen University.]

In Fig. 24 we ill.u.s.trate the Diaphone in the Hope-Jones organ built for Aberdeen University, Scotland. The action is as follows:

Wind from the organ bellows enters the pipe foot F, and raises the pressure in the chamber C. The air in the chamber will press upon the back of the valve V, tending to keep it closed. It will press also upon the bellows or motor M, and as this bellows has a much larger area than that of the valve, it will instantly collapse, and, through the medium of the tail piece T, will pull the valve V off its seat and allow the compressed air in the chamber C to rush into the resonator or pipe P. Owing to the inertia of the column of air contained in the pipe P, a momentary compression will take place at the lower end of the pipe, and the pressure of the air inside the motor M will, in consequence, be raised. The motor having now increased pressure both sides, will no longer keep the valve off its seat, and the spring S will open the motor and close the valve. The compression caused by the admission of the puff of air into the lower parts of the pipe P will be followed by the usual rarefaction, and as this rarefaction will exhaust or suck the air from the inside of the motor M, the valve will again be lifted from its seat, and the cycle of operations will be repeated as long as the wind supply is kept up. A series of regular puffs of wind will thus be delivered into the lower part of the resonator or pipe, resulting in a musical note.

Figs. 25, 26, 27 represent the first Diaphone heard in a public building in this country, namely that of a model sounded in St.

Patrick's Cathedral, New York City, in 1905. In this form of Diaphone the pressure of air operating the Diaphone has been varied between 10 inches and 500 inches, without perceptible variation in the pitch of the note emitted.

[Ill.u.s.tration: Figs. 25, 26, 27. Diaphone in St. Patrick's Cathedral, New York]

Referring to Fig. 25, the chamber WW is supplied with air under pressure whenever the organist presses a key or pedal calling into use this particular note. The pressure of air enters through the circular engine supply port S, thus raising the pressure in the chamber C and forcing in an upward direction the aluminum piston P through the medium of the division D (colored black), which forms a portion of the aluminum piston.

When the lower edge of the piston has risen a certain distance it will uncover the circular engine exhaust port E, and will allow the compressed air to escape into the atmosphere. At this moment the rise of the piston will have closed the engine supply port S.

The momentum acquired by the piston (see Fig. 27) will cause it to travel upward a little further, and this upward travel of the division D will cause a compression of air to take place at the foot of the resonator or pipe R. This compression will be vastly increased through the simultaneous opening of the eight circular speaking ports SP.

The pressure of the compressed air at the foot of the resonator E will now by acting on the upper surface of the division D depress the aluminum piston until the engine supply port S is again opened.

By this time the compression at the foot of resonator R will have traveled up the pipe in the form of a sound wave, and will have been followed by the complementary rarefaction. This rarefaction on the upper side will render more effective the pressure of the compressed air again admitted through the engine supply port S on the underside of division D.

It will be seen that this cycle of operations will be repeated as long as the organist holds down his pedal or key admitting compressed air to the chamber W.

As the aluminum piston P is very light and is in no way impeded in its movement or swing, the speed of its vibration, and consequently the pitch of the note emitted, will be governed by the length of the resonator or pipe R.

The tone given by this particular form of Diaphone possesses a peculiar sweetness in quality, while the power is limited only by the pressure of air used to operate it.

[Ill.u.s.tration: Fig. 28. Diaphone in the Auditorium, Ocean Grove, N. J.]

In Fig. 28 we give an ill.u.s.tration of the form of Diaphone used in the Hope-Jones Unit organ at the Auditorium, Ocean Grove, N. J.

P is a pallet controlling the admission of air into the body of the pipe P|1|. M is a motor adapted for plucking open the pallet P through the medium of strap _s_. The box B is permanently supplied with air under pressure from the bellows. When the valves V and V|1| are in the position shown in the drawing, the Diaphone is out of action, for the wind from the box B will find its way through the valve V (which is open) into the interior of the motor M.

When it is desired to make the note speak, the small exterior motors M|1| and M|2| are simultaneously inflated by the electro-pneumatic action operated by depressing the pedal key. The valve V will thereupon be closed and the valve V|1| be opened. As the pressure of air inside the motor M will now escape into the pipe or resonator P|1|, the motor will collapse and the pallet P will be opened in spite of the action of the spring S which tends to keep it closed.

The wind in the box B will now suddenly rush into the lower end of the pipe P|1|, and by causing a compression of the air at that point will again raise the pressure of the air inside the motor M. The pallet will thereupon close and the cycle of operations will be repeated--thus admitting a series of puffs of wind into the foot of the pipe P|1| and thereby producing a musical tone of great power.

As the valve V|1| is open, the sound waves formed in the pipe P|1| will govern the speed of vibration of the motor M. It will thus be obvious that the Diaphone will always be in perfect tune with the resonator or pipe P|1|, and that the pitch of the note may be altered by varying the length of the pipe.

[Ill.u.s.tration: Fig. 29. Diaphone in St. Paul's Cathedral, Buffalo, N.

Y.]

In Fig. 29 will be found an ill.u.s.tration of the Diaphone (or valvular reed) used in the Hope-Jones organ at St. Paul's Cathedral, Buffalo, N.

Y.

Upon depressing a key, wind is admitted into the box B. Pressing upon the valve V it causes it to close against its seat in spite of the action of the spring S. This, however, does not take place until a pulse of air has pa.s.sed into the foot of the pipe P, thereby originating a sound wave which in due time liberates the valve V and allows the spring S to move it off its seat and allow another puff of air to enter the pipe P. By this means the valve V is kept in rapid vibration and a powerful tone is produced from the pipe P. At Middlesborough, Yorkshire, England, Hope-Jones fitted a somewhat similar Diaphone of 16 feet pitch about 1899, but in this case the resonator or pipe was cylindrical in form and measured only 8 feet in length.

In Fig. 30 will be found another type of Diaphone in which the tone is produced through the medium of a number of metal b.a.l.l.s, covering a series of holes or openings into the bottom of a resonator or pipe, and admitting intermittent puffs of air.

[Ill.u.s.tration: Fig. 30. Diaphone Producing Foundation Tone]

The action is as follows. Air under pressure enters the chamber B through the pipe foot A, and pa.s.sing up the ports C, C|1|, C|2|, etc., forces the metal b.a.l.l.s D, D|1|, D|2|, etc., upwards into the chamber E; the bottom end of the resonator or pipe. The pressure of air above the b.a.l.l.s in the resonator E, then rises until it equals or nearly equals the pressure of air in chamber B. This is owing to the fact that the column of air in the pipe or resonator E possesses weight and inertia, and being elastic, is momentarily compressed at its lower end. This increased pressure above the b.a.l.l.s allows them to return to their original position, under the influence of gravity. By the time they have returned to their original position, the pulse of air compression has traveled up the pipe in the form of a sound wave, and the complementary rarefaction follows.

The cycle of movement will then be repeated numerous times per second, with the result that a very pure foundation tone musical note will be produced.

The Diaphone is tuned like ordinary flue pipes and will keep in tune with them; the pressure of wind (and consequently the power of the tone) may be varied without affecting the pitch. The form of the pipe or resonator affects the quality of the tone; it may be flue-like or reedy in character, or even imitate a Pedal Violone, a Hard and Smooth Tuba, an Oboe, or a Clarinet.

In closing this chapter, the writer desires to express indebtedness for much of the material therein to the comprehensive "Dictionary of Organ Stops," by James Ingall Wedgwood, Fellow of the Society of Antiquaries, Scotland, and Fellow of the Royal Historical Society (published by the Vincent Music Co., London, England). Although the t.i.tle is somewhat forbidding, it is a most interesting book and reveals an amount of original research and personal acquaintance with organs in England and the Continent that is simply marvelous. It ought to be in the library of every organist.

[1] Broadhouse, J., "Musical Acoustics," p. 27.

[2] Mr. Skinner has built some of the finest organs in this country.

[3] Much of Roosevelt's finest work is now being improved by various builders by leathering the lips.

[4] The "Harmonic" principle is described in Dom Bedos' book, published in 1780, as applied to reeds, and Dr. Bedart states that this principle was applied to flutes as early as 1804.

[5] That is to say, the pipes are made double the length actually required, but are made to sound an octave higher by means of a hole pierced half-way up the pipe.

[6] Wedgwood; "Dictionary of Organ Stops," p. 150.

[7] Wedgwood: _Ibid_., p. 153.

[8] Wedgwood: _Ibid_., p. 151.

[9] Wedgwood: _Ibid_. p. 153.

[10] "The Hope-Jones pattern of Muted Viol is one of the most beautiful tones conceivable."--Wedgwood: "Dictionary of Organ Stops," p. 173.