The Recent Revolution in Organ Building Part 5

Church, London, England, in the year 1731.

The "nag's head" Swell, with its great sliding shutter, rapidly gave place to the "Venetian" Swell shades, used almost universally to this day. At the beginning of the period under consideration Swell boxes were almost invariably made of thin boards and their effect upon the strength of the tone was small. Willis was one of the first to realize the artistic possibilities of the Swell organ and in almost all his organs we find thick wooden boxes and carefully fitted shutters, and often an inner swell box containing the delicate reeds, such as the Vox Humana and Oboe.

Many of the leading organ builders now employ this thicker construction, and it is no uncommon thing to find Swell boxes measuring three inches in thickness and "deadened" with sawdust or shavings between the layers of wood of which they are formed.

A few organs of Hutchings and other makers are provided with a double set of shutters, so that sound waves escaping through the first set are largely arrested by the second. The _crescendo_ and _diminuendo_ are thus somewhat improved.

By the adoption of scientific principles Hope-Jones has multiplied the efficiency of Swell boxes tenfold. He points out that wood, hitherto used in their construction, is one of the best known conductors of sound and should, therefore, not be employed. The effects produced by his brick, stone and cement boxes (Worcester Cathedral, England; McEwan Hall, Edinburgh, Scotland, Ocean Grove, New Jersey, etc.) mark the dawn of a new era in Swell-box construction and effect. It is now possible to produce by means of scientific Swell boxes an increase or diminution of tone amounting to many hundred per cent.

We have heard the great Tuba at Ocean Grove, on 50-inch wind pressure, so reduced in strength that it formed an effective accompaniment to the tones of a single voice.

The Hope-Jones method seems to be to construct the box and its shutters (in laminated form) of brick, cement or other inert and non-porous material, and to subst.i.tute for the felt usually employed at the joints his patented "sound trap." This latter is so interesting and of such import in the history of organ building that we append, on the next page, ill.u.s.trations and descriptions of the device.

If a man should stand at one end of the closed pa.s.sage (C) he will be able to converse with a friend at the other end of the pa.s.sage (D).

The pa.s.sage will in fact act as a large speaking tube and a conversation can be carried on between the two individuals, even in whispers (Figure 12).

This pa.s.sage is a.n.a.logous to the opening or nick between Swell shutters of the ordinary type.

If a man should stand in room 1 at A, he will be able to see a friend standing in room 4 at B, but the two friends will not be able to converse. When A speaks, the sound waves that he produces will spread out and will fill room 1. A very small percentage of them will strike the doorway or opening into room 2. In their turn these sound waves will be diffused all through room 2, and again but a small percentage of them will find access into room 3. The sound waves will by this time be so much attenuated that the voice of the man standing in room 1 will be lost. Any little tone, however, that may remain will become dissipated in room 3, and it will not be possible for a person standing in room 4 to hear the voice.

[Ill.u.s.tration: Fig. 12. The Principle of the Sound Trap]

This plan ill.u.s.trates the principle of the sound trap joint.

Figure 13 shows in section the joint between two Swell shutters. A small proportion of the sound waves from inside the Swell box striking the sound trap joint, as indicated by the arrow, will pa.s.s through the nick between the two shutters, but these sound waves will become greatly weakened in charging the groove A. Such of the sound waves is pa.s.s through the second nick will become attenuated in charging the chamber B. They will be further lost in the chamber C, and practically none will remain by the time the chamber D is reached.

It is Hope-Jones' habit to place the shutters immediately above the pipes themselves, so that when they are opened the Swell box is left practically without any top. It is in such cases not his custom to fit any shutters in the side or front of the Swell box.

[Ill.u.s.tration: Fig. 13. Sound Trap Joint]

To relieve the compression of the air caused by playing for any length of time with the shutters closed, he provides escape valves, opening outside the auditorium. He also provides fans for driving all the cold air out of the box before using the organ, thus equalizing the temperature with the air outside--or he accomplishes this result through the medium of gas, electric or steam heaters, governed by thermostats.

The Hope-Jones Vacuum Swell Shutters, with sound-trap joints, are shown in Figures 14 and 15.

It is well known that sound requires some medium to carry it. Readers will doubtless be familiar with the well-known experiment ill.u.s.trating this point. An electric bell is placed under a gla.s.s dome. So long as the dome is filled with air the sound of the bell can be heard, but directly the air is pumped out silence results, even though it can be seen that the bell is continuously ringing. As there is no air surrounding the bell there is nothing to convey its vibrations to the ear.

That is why the hollow swell shutter, from the interior of which the air has been pumped out, is such a wonderful non-conductor of sound.

The shutters shown in Figures 14 and 15 are aluminum castings.

Ribs R|1| and R|2| are provided to support the flat sides against the pressure of the atmosphere, but each of these ribs is so arranged that it supports only one flat side and does not form a means of communication between one flat side and the other. Thus R|1| supports one flat side whilst R|2| supports the other. The aluminum shutters are supported by means of pivot P.

[Ill.u.s.tration: Figs. 14-15. The Vacuum Shutter]

They are very light and can therefore be opened and closed with great rapidity.

A very thin vacuum shutter forms a better interrupter of sound waves than a brick wall two or three feet in thickness.

When partially exhausted the aluminum shutters are dipped into a bath of sh.e.l.lac. This effectually closes any microscopic blow-hole that may exist in the metal.

The use of Swell boxes of this vastly increased efficiency permits the employment of larger scales and heavier pressures for the pipes than could otherwise be used, and enormously increases the tonal flexibility of the organ.

It also does away with the need for soft stops in an organ, thus securing considerable economy. Where all the stops are inclosed in cement chambers (as in the case of recent Hope-Jones organs) and where the sound-trap shutters are employed, _every_ stop is potentially a soft stop.

CHAPTER VIII.

A REVOLUTION IN WIND SUPPLY.

Prior to the construction of the above-named organ at Birkenhead, England, it had been the custom to obtain or regulate the pressure of wind supplied to the pipes by means of loading the bellows with weights. Owing to its inertia, no heavy bellows weight can be set into motion rapidly. When, therefore, a staccato chord was struck on one of these earlier organs, with all its stops drawn, little or no response was obtained from the pipes, because the wind-chest was instantly exhausted and no time was allowed for the inert bellows weights to fall and so force a fresh supply of air into the wind-chests.

BELLOWS SPRINGS VERSUS WEIGHTS.

In one of Hope-Jones' earliest patents the weights indeed remain, but they merely serve to compress springs, which in turn, act upon the top of the bellows.

Before this patent was granted he had, however, given up the use of weights altogether and relied entirely upon springs.

This one detail--the subst.i.tution of springs for weights--has had a far-reaching effect upon organ music. It rendered possible the entire removal of the old unsteadiness of wind from which all organs of the time suffered in greater or less degree. It quickened the attack of the action and the speech of the pipes to an amazing extent and opened a new and wider field to the King of Instruments.

In the year 1894 John Turnell Austin, now of Hartford, Conn., took out a patent for an arrangement known as the "Universal air-chest." In this, the spring as opposed to the weight is adopted. The Universal air-chest forms a perfect solution of the problem of supplying prompt and steady wind-pressure, but as practically the same effect is obtained by the use of a little spring reservoir not one hundredth part of its size, it is questionable whether this Universal air-chest, carrying, as it does, certain disadvantages, will survive.

INDIVIDUAL PALLETS.

Fifty years ago the pallet and slider sound-board was well nigh universally used, but several of the builders in Germany, and Roosevelt in this country, strongly advocated, and introduced, chests having an independent valve, pallet or membrane, to control the admission of wind to each pipe in the organ.[1]

In almost all of these instances small round valves were used for this purpose.

A good pallet and slider chest is difficult to make, and those constructed by indifferent workmen out of indifferent lumber will cause trouble through "running"--that is, leakage of wind from one pipe to another. In poor chests of this description the slides are apt to stick when the atmosphere is excessively damp, and to become too loose on days when little or no humidity is present.

Individual pallet chests are cheaper to make and they have none of the defects named above. Most of these chests, however, are subject to troubles of their own, and not one of those in which round valves are employed permits the pipes to speak to advantage.

Willis, Hope-Jones, Carlton C. Mich.e.l.l and other artists, after lengthy tests, independently arrived at the conclusion that the best tonal results cannot by any possibility be obtained from these cheap forms of chest. Long pallets and a large and steady body of air below each pipe are deemed essential.[2]

HEAVY WIND PRESSURES.

As previously stated, the vast majority of organs built fifty years ago used no higher wind pressure than 3 inches. Hill, in 1833, placed a Tuba stop voiced on about 11 inches in an organ he built for Birmingham Town Hall (England), but the tone was so coa.r.s.e and blatant that such stops were for years employed only in the case of very large buildings.[3] Cavaille-Coll subsequently utilized slightly increased pressures for the trebles of his flue stops as well as for his larger reeds. As a pioneer he did excellent work in this direction.

To Willis, however, must be attributed greater advance in the utilization of heavy pressures for reed work. He was the first to recognize that the advantage of heavy wind pressure for the reeds lay not merely in the increase of power, but also in the improvement of the quality of tone. Willis founded a new school of reed voicing and exerted an influence that will never die.

In organs of any pretensions it became his custom to employ pressures of 8 to 10 inches for the Great and Swell chorus reeds and the Solo Tubas in his larger organs were voiced on 20 or 25 inches.

He introduced the "closed eschallot" (the tube against which the tongue beats in a reed pipe) and created a revolution in reed voicing. He has had many imitators, but the superb examples of his skill, left in English Cathedral and town hall organs, will be difficult to surpa.s.s.

Prior to the advent of Hope-Jones (about the year 1887) no higher pressure than 25 inches had, we believe, been employed in any organ, and the vast majority of instruments were voiced on pressures not exceeding 3 inches. Heavy pressure flue voicing was practically unknown, and in reeds even Willis used very moderate pressures, save for a Tuba in the case of really large buildings.