_TWO-MANUAL ORGANS._
THIS treatise must not close without some reference to organ work of a
more advanced kind than that which we have taken as the groundwork or
medium of our hints on this subject.
Some of our readers may very naturally wish to understand the
construction of an organ with two or more manuals and a pedal with
separate pipes; and this implies a description of coupling movements
and of the swell-box and its appliances.
In the first place, let us remark that as the swell-organ is a modern
invention, innumerable examples of organs with more than one manual and
with numerous stops, but entirely without the swell, were in existence
in England up to a recent period, and are still to be found in every
part of the continent of Europe. A great number of the most renowned
organs of Germany and of Holland, organs furnished with four manuals
and an immense aggregate of pipes, are without the swell to this day.
This is not the place to discuss the question whether the introduction
of the swell, as the second division of an organ with only two
manuals, has been an unmixed advantage, and whether it has or has
not tended to raise the standard of organ music and organ-playing in
England. But some few musicians may agree with the present writer that
it is quite possible to sacrifice sound principles of organ-building to
the prevailing worship of the pretty and fanciful effects of the swell,
and may even go so far as to regret, with him, the supersession of the
old "choir organ," with its sweet tranquil tone and quiet cheerful
brightness. We ourselves make no secret of our wish that in the design
and erection of organs with only two manuals, the second manual should
act upon a choir organ, while the swell should be reserved for those
instruments in which a third manual is introduced. But we are quite
aware that these views will be received with derision by a great
majority of persons, who have become accustomed to the constant use of
the swell and of the pedal Bourdons which characterizes the playing of
many English organists on modern English organs.
Quite apart, however, from these views, which must be taken for what
they are worth, there are reasons why any reader, resolving from the
first to construct a small organ with two manuals for chamber use, will
do well to resist the temptation to introduce the swell. These reasons
will become apparent if we sketch out one or two plans for such chamber
organs, and we should only occupy space needlessly by stating them in
advance.
Resolving, then, to indulge ourselves with two manuals, but compelled
to be economical of space and of pecuniary outlay, we decide at once
to plant all the pipes, belonging to both manuals alike, upon a single
sound-board, and by the system of borrowing to avoid the reduplication
of large pipes in the bass octave.
To our original design of five stops on a single manual, let us suppose
that we have added three, played by a second key-board. We must assume
that the five stops belonging to the first manual (the lower), will be
all throughout, and may be something like this, viz.: an open Diapason
with wood bass octave; a Clarabella, with stopped bass octave; a
Principal, Flute, and 2-feet stop as before. Then the second or upper
manual should have some such stops as these: Stopped Diapason, the
bass octave borrowed from that of the Clarabella; Dulciana to Tenor C;
Gems-horn, or some other light 4-feet stop, the bass octave borrowed
from that of the Flute or Principal.
As the sound-board will have two grooves for each note throughout
its whole extent, namely 108 grooves if the manuals are of the usual
compass, its length might be unwieldy and inconvenient, ill adapted
to the size of ordinary rooms. We must strongly recommend, therefore,
that the arrangement shown in Fig. 39 (see p. 112) be adopted. On the
front portion, _b c_, containing eighty-four grooves, and carrying
eight sliders, all the stops from Tenor C to top F may be planted. On
the back portion, _a b_, which will have twenty-four grooves only, all
the bass pipes will be placed, unless, indeed, we assume that the large
open 8-feet pipes are conveyanced off. This back portion will carry one
slider for this open bass, one for each of the 4-feet and 2-feet stops,
and two pairs of twin sliders, placed close together, for the borrowed
stopped bass and borrowed 4-feet bass.
Our readers may feel confidence in the directions now given if we say
that we are describing an organ built by ourselves and now in our
possession.[3] The sound-board, admitting of eighty-four grooves in
its front division, is 5 feet 3 inches long, and its seven sliders (we
have no stopped Flute), with the bearers, occupy a width of 16 inches;
but the 4-feet octave of the Open Diapason, and six pipes of the
Dulciana, are brought into sight as a "speaking front," and therefore
fill no space on the board itself. The back part of the board, with
four sliders (two of them twin), has also a width of about 16 inches,
our large open wood bass being on a board at a lower level, as in Fig.
10. Thus the whole board, carrying practically eight stops (one of our
stops is of two ranks, viz. a Twelfth and Fifteenth) throughout, is 5
feet 3 inches long and 32 inches wide.
[3] This organ is sketched in the frontispiece.
We hope we have said quite enough in former pages of roller boards and
backfalls to enable any intelligent reader to devise for himself the
double action of such an organ. An inspection of Figs. 37, 38, and 39
may suggest ideas to him. An essential point is that everything should
be within reach if defects should require attention; and access to the
back as well as to the front of such an organ is indispensable.
A word about the borrowing. It is plainly not enough to groove the two
channels of each note together in the bass, as in the case of a single
manual. If this were done the wind would fill the _whole_ of the two
channels upon lowering a key in the bass octave of either manual, and
_all the stops_ of which the sliders happened to be drawn at the time
would speak together. Thus our purpose of borrowing one particular stop
would be defeated. We must effect it thus: the twin sliders will be
closely contiguous, and will only be separated by short pins of brass
or iron let into the table, to prevent the friction of actual contact.
Thus the two holes which are to be brought into connection are near
to each other, and the communicating groove will be short. If this
is cut in the upper board itself it must be neatly executed, and the
bottom of the groove must be level and smooth. Over each of the two
holes within the groove so cut must be placed a valve, consisting of a
small piece of pallet leather covering the hole completely, and rising
with complete freedom by a hinge along its edge, like the clacks of
the bellows. Each pair of holes being furnished with these valves the
grooves are roofed in and the pipes planted, as described in earlier
pages of this book. On lowering one of the keys the wind will affect
the borrowed pipe only, since the little valve will stop the twin
hole and prevent the flow of air through it into the channel. If the
key corresponding to the same note be pressed down on both manuals,
then both the little valves will be blown open by the wind; but if
all the channels, grooves, and holes be of ample size, so that there
is no throttling of the wind, the speech of the pipe will be entirely
unaltered, since it will only receive a given _quantity_ of wind
through the perforation in its foot, and this wind will be of the same
_weight_ or _pressure_ as before.
The borrowing grooves may be cut in the under surface of a separate
board, which will then form a roof or cover to the several pairs of
valves arranged over the holes on the upper surface of the sound-board
itself. Or this borrowing-board may be put together with bars, cheeks,
and an upper table like a light sound-board. The essential point is
that all the openings be of ample size, and that the valves fly open
widely at the slightest breath of wind, and close the holes as promptly
when the wind is withdrawn. If due attention is given to all this no
failure need be anticipated with the borrowed basses.
We have proposed the lower key-board as "Manual I.," in accordance
with the German usage, and because that arrangement will facilitate
some of our mechanism, for instance, the pulling down by the pedals of
the bass notes. But lovers of old English organs, among whom we must
reckon ourselves, may prefer to make Manual I. the upper manual of the
two. A beautiful instrument of this class, built by the late J. C.
Bishop, stands in the chapel of Jesus College, Cambridge, and was the
gift of an accomplished amateur, whose performances on it are still
remembered.[4] The same gentleman was the possessor of a chamber organ
of exquisite tone by Bernhard Schmidt, of such remarkable composition
that it merits description here. The lower manual, or Choir, had three
stops, an Open Diapason, a Stopped Diapason, and a Principal, all made
of oak, and of extreme delicacy and beauty. The upper manual, or Great,
had likewise three stops, all metal, namely, Stopped Flute, Fifteenth,
and Mixture of two ranks (19th and 22nd in the bass, 12th and 17th in
the treble). The Stopped Diapason could also be played upon this manual
by borrowing. A coupler united the lower to the upper at pleasure,
and then the "Full Organ" was produced upon the upper manual with an
astonishing effect of sprightliness and brightness. Such an organ as
this, with some changes (its key-boards were very antiquated, and so
high from the ground that the player was perforce erect), might afford
an admirable model for imitation.
[4] The late Sir John Sutton, Bart., author of "A Short Account of
Organs built in England from the Reign of King Charles II. to the
Present Time." Masters, 1847.
Let us add that if pedal notes of 16-feet tone are added to an
organ of this class, namely of two manuals, Great and Choir, only
twelve large pipes will be necessary, even though the compass of the
pedal-board be of thirty notes complete. This great economy of space
and outlay will be secured thus: 1st, by making the pedals pull down
on the chief manual throughout their whole extent as before; 2nd, by
adapting the twelve deep pipes to the lower octave of the pedals, and
by making their upper octave and a half pull down upon the lowest
keys of the second manual. A moment's reflection will show that the
16-feet tone is thus obtained throughout the whole compass, and no
inconvenience whatever will ensue to the player.
The mode of introducing the large bass pipes, and of pulling down as
above, will be described before we conclude this work.
Still desiring to erect a _chamber_ organ, and, therefore, to be chary
of space and cost, we must now show how the swell-box may be included
in our design.
We shall suppose that the organ has been completed so far as the lower
manual is concerned, with all that pertains to it, according to the
rules which have now been given at length and in detail. In laying it
out we must assume that care has been taken to give increased size to
the bellows, and to arrange the frame for the reception of a second
sound-board.
We feel it due as well to our readers as to ourselves to explain that
we confine ourselves in all that follows to a description of work done
by ourselves in our own workshop.
We shall place only three stops in our swell, which will have a
compass of forty-two notes, from Tenor C to top f. The stops will be
a Diapason in wood, partly stopped, and the rest open; a Flute of
4-feet tone in wood, open throughout; and a Gamba of reedy quality, in
metal, of 8-feet pitch, but only descending to Fid. G., 3 feet, the
remaining notes being grooved to No. 1. This curtailment is greatly to
be regretted, but such imperfections are among the objections to the
swell-box, which would assume dimensions inconsistent with a _chamber_
organ if an attempt were made to give full compass to its 8-feet stops.
The sound-board for these three stops will be only 2 feet 9 inches in
length, and 1 foot in width; but the upper boards must have an ample
margin or surplus in both directions to afford support for the box
which will rest upon them.
This box must be made of thick stuff, say 1-1/2 inch deal; it will
therefore be very heavy, and care must be taken to provide for its
weight in planning the frame. It should be put together with screws,
so that it can easily be taken to pieces for transit, and it is usual
to line the whole of its interior with sheets of thick brown paper,
applied with glue. It will be very convenient, if access can be had to
the back of the organ, to fit the back of the box with hinged doors,
or to make the back removable like a shutter; in this case the pipes
should be planted so as to present themselves readily to the tuner.
If access to the back cannot be had, then a space is inevitable in the
middle of the organ for a passage-board, on which the tuner may stand,
or at least place his foot, while he removes the front shades in order
to reach the pipes planted accordingly. In the swell-boxes of church
organs the sides of the box are generally fitted as doors; then, the
pipes being planted with the tallest in the centre, diminishing in
height to each end, half of them can be tuned at one operation. When
the pipes are thus planted, the top of the box will slope towards each
side from a central ridge, like the roof of a house.
[Illustration: Fig. 50.]
We cannot doubt that many of our readers have had, or may have,
opportunities of examining the construction of the shutters or shades
of a swell-box. We have sketched it, however, in Fig. 50. The shades
are 6 inches in breadth, and of the same thickness as the rest of the
box, and each shade turns on pins let into the ends of it at a distance
of 2 inches from its upper edge. These pins work in notches cut in the
cheeks of the box, so formed that any shade may be easily lifted out
and replaced. The edges of the shades are bevelled to half a right
angle so that they overlap when closed, and the bevelled surfaces are
faced with leather or cloth to shut in the sound more effectually.
[Illustration: Fig. 51.]
The mode of opening the shades, and so producing a _crescendo_, is
shown in Fig. 51. _a_, _b_, _c_ are arms of oak, morticed into the
shades at the level of the pins, viz. 2 inches from the upper line;
_d e_ is a long rod or tringle of wood, connecting all these arms by
pins passing through them and itself. It is evident that by drawing up
this rod at its top, or by pushing it up from below, we shall open all
the shades at once, and as they are hung on axes placed at one-third
of their breadth, they will close by their own weight when released.
The leverage by which this movement is brought under the control of
the player may be safely left to the inventive powers of the reader.
It is usual to give promptness to the return of the swell-pedal, and
therefore to the closing of the shades, by attaching a strong spiral
spring to the pedal, and to some firm point in the frame.
[Illustration: Fig. 52.]
As the swell-box is at the back of the instrument, its key-action will
have to pass or cross that of the Great organ. The way in which this
will be effected must depend a little upon circumstances--for instance,
upon the length of the key-tails in the two manuals. If the swell
manual acts by squares and trackers, while the Great has backfalls
and stickers, the small trackers, being thin ribands of wood, can be
easily made to pass between the Great stickers. Or if the swell-keys
act on backfalls, these backfalls may be thinned down behind the line
of key-tails, so as to allow the stickers of the lower manual to pass
between them. This may be understood from Fig. 52, though that figure
refers to another subject. The worst plan of all is to make the lower
stickers pass through holes or mortices in the upper key-tails, since
this prevents the removal of the upper key-board without a disturbance
of the whole action.
We believe that these constructive details contain in themselves the
grounds on which we based our advice to hesitate before including a
swell-box in the design for a small chamber organ. It has been made
apparent that it brings with it a considerable increase of bulk,
weight, and complication, and that it cannot possess the full compass.
We must add that if the bellows are worked by the foot, the use of the
swell-pedal at the same time is of course impossible.
The large swells of church organs owe their grandeur of effect to their
reed-stops; the trumpet, of which the oboe is a soft echo and our
little gamba a faint and humble imitation, the horn or cornopean, and
the double trumpet or bassoon, a stop of 16-feet pitch. All reed-stops
are quite beyond the range of amateur construction, and each of the
above will cost about £25 if purchased from a good maker and made of
first-class material. Beautiful as such stops are when made and voiced
by highly-skilled workmen, they may easily be unpleasing and even
offensive.
Let us add that the twelve notes of the swell manual, below Tenor C,
may be made to act on the lower manual by a "choir coupler" (see next
section, and Fig. 52); or, if there is a complete pedal Sub-bass or
Bourdon of twenty-five or more notes, the silent keys of the swell
manual may borrow the pedal notes from CC, 8-feet tone upwards. An
easy mechanical movement of squares and trackers will effect this.
Two manuals imply couplers, though we greatly regret the incessant use
of these contrivances by modern organists.
[Illustration: Fig. 53.]
We shall treat, very briefly, of couplers under three heads, viz. the
coupling of--
(_a_) Upper Manual to Lower Manual.
(_b_) Lower Manual to Upper Manual.
(_c_) Manuals to Pedals.
(_a_) The common Tumbler coupler is represented in Fig. 53. _a_ is
a slender bridge, having as many notches as keys in the manual,
and fitted with short stickers called tumblers. These tumblers, or
stickers, are generally rectangular in section, and they must fit the
notches neatly but with freedom of motion; the notches are closed in by
a tringle of wood glued over them, thus forming a series of mortices;
and each sticker has a little pin, or a pair of pins, to prevent it
from falling out of its notch or mortice. Or, the tumblers may be made
from round rods, and may pass through round holes in the bridge. They
are well blackleaded in either case. Now if this bridge, with its
tumblers, is placed between the manuals near their hinder extremities,
if the length of the tumblers is equal to the interval between the
upper and lower key-tails, it is evident that on pressing down a key of
the lower manual the tumbler will push up the tail of the corresponding
key on the upper manual, and so on throughout the full compass of both.
To reverse this, and to leave the manuals separate and independent as
before, the bridge is made to take a quarter of a revolution in sockets
fitted to carry its ends, which are rounded or turned in the lathe; the
tumblers, by this partial revolution, are then no longer perpendicular,
but parallel to the key-tails, as shown by the dotted lines in the
figure, and cease to be touched by them. On the whole, this is the
simplest form of swell-coupler.
[Illustration: Fig. 54.]
The tumblers may also be placed on or off by causing the bridge to
slide between guides for a distance of 1 inch or 2 inches. When the
bridge is pushed back by drawing a stop-handle (which acts upon a
horizontal trundle with arms and traces to give the sliding motion),
the tumblers act on the key-tails; when it is drawn forward by
thrusting in the stop, they fall into a hollow cut in the key-tails,
and are too short to be of use. The hollow in the key-tails is
bevelled, and the inclined plane so formed is leathered and blackleaded
(see Fig. 54).
[Illustration: Fig. 55.]
The ram coupler, Fig. 55, acts in a way closely resembling the last.
Instead of tumblers, the bridge carries a set of short backfalls,
turning on a wire as usual, and cut at the free end into a circular
form. The sliding of the bridge brings these circular ends into contact
with the key-tails of both manuals, or places them in a hollow cut
in the keys, bevelled, leathered, and blackleaded as before. The
ram-coupler can be used between manuals arranged too closely to admit
of tumblers.
(_b_) It will facilitate our description of the choir-coupler and
pedal-couplers if we here point out that if a bridge with backfalls
(or squares) be made to rise or fall 1/2 inch or more at pleasure, the
action connected with it will be thrown into or out of gear at the will
of the player. If, in Fig. 32, for instance, the bridge _g_ be made to
rise 1/2 inch by drawing a stop-handle, the stickers _e_ will then be
too short by 1/2 inch, or the pull-downs _h_ will be too long in an
equal degree, and the manual will be silenced.
[Illustration: Fig. 56.]
An easy way of making such a bridge rise and fall is shown in Fig. 56.
The bridge _a_, which cannot be too solid and heavy, is held between
guides, _c d_, which are blackleaded and accurately adjusted. At each
end of the bridge is fitted a little roller or wheel of box-wood,
turning freely on a pin. To the frame below is fitted another such
roller, or two, as in the figure. Between these two or three rollers,
at each end of the bridge, an inclined plane of wood, _e_, is made to
traverse by means of a horizontal trundle and arms. It will be seen at
a glance that when the inclined plane is pushed between the rollers
by drawing or thrusting in a stop-handle, it lifts the bridge between
the guides and dislocates the action; when it is withdrawn, the bridge
resumes its place by its own weight, and the action is again in order.
It is now easy to understand the construction of the remaining
couplers. The choir-coupler (Fig. 52, p. 152), has two bridges, _x_,
_y_, with two sets of short backfalls and communicating stickers. If
the bridges are fixed, then on depressing any key on the upper manual
its tail raises the backfall, which presses down the lower backfall,
which in its turn pushes up the tail of the lower key and causes the
note to be heard. If the upper bridge be made to rise or the lower to
fall 1/2 inch, then the keys are at once disconnected.
(_c_) The coupling of manuals to pedals is generally effected by rising
and falling bridges, carrying backfalls which push up the tails of
the keys. These bridges are arranged one above the other beneath the
keyboards in large organs with three or four manuals, each bridge
bringing its own manual into connection with the pedals by the movement
already described. One roller-board (the rollers are often of iron for
the sake of compactness) suffices for all the sets of backfalls, and
the stickers (in this case generally flat strips of wood) pass through
mortices cut in the tails of the lower keys to act upon the tails of
the keys to which they belong.
The reader will easily perceive from these hints how the pedals may be
made to act through their whole extent upon one of our manuals, and
through only a part of their extent upon the other manual, as we have
hinted at page 148. There will be two bridges, one over the other, and
a very little ingenuity will be required to plan the roller-board so
that the central C of the pedals shall pull down the lowest C of the
second manual (be it upper or lower), and thus give the octave below
(or 16-feet pitch) without additional pipes from that note upwards.
But this, perhaps, belongs to the subject of the pedal organ, which we
reserve for the conclusion of this book.
It is right to add here that in old-fashioned organs, both in England
and on the Continent (where many such instruments remain unaltered),
the manuals were made to couple by being drawn out or pushed in about
1/2 inch. A spur or protuberance of wood was glued to the upper part of
the tail of each key, and a similar spur to the under part of the tail
of the key in the manual above. These spurs had rounded ends covered
with leather. On shifting one of the key-boards backwards or forwards
the spurs met each other, and the coupling was effected. Or the spurs
were glued under the front of each key, immediately behind the beading
of the key-frame, and upon the upper surface of each key in the manual
beneath it, and a similar shifting brought about a like result. We
see no objection to this very simple old-fashioned arrangement strong
enough to induce us to discard it from consideration.
The common type of small church organ with Great and Swell (throughout)
would be vastly improved by the introduction of a manual between the
other two, having no stops of its own, but coupled to both by such
spurs. Instead of two qualities of sound, namely Swell alone and
Great and Swell combined (the incessant use of the coupler being
the inveterate habit of most players), we should have three: Great
alone, Swell alone, and combination of Great and Swell. This obvious
improvement could be introduced into new organs or added to existing
instruments at a very small cost. There should be a coupler to connect
this Combination Manual with the pedals.
It is undeniable that the addition of a pedal organ with a Sub-bass or
Bourdon of 16-feet tone is a very important and valuable improvement
to any organ, large or small. It gives a dignified cathedral-like
solemnity and grandeur which every ear can appreciate. We shall bring
our treatise to a close by a few remarks upon it.
1. The pipes will be made precisely like those of the Stopped Diapason,
of which they may be regarded as a continuation, and they should
be of stout material, the last four or five of inch stuff, then
three-quarters to the twelfth or thirteenth note above.
On the question of scale the most diverse opinions have found favour
of late years. A writer whose _dicta_ are entitled to respect[5] urges
that the lowest pipe (CCC, 16-feet tone) should have the enormous if
not preposterous scale of 11-1/2 by 13 inches inside measurement, and
that the next six pipes above it should be in proportion. After that,
he says, a smaller scale may suffice. It is clear that if this ruling
be correct we may dismiss the idea of introducing a Sub-bass into our
chamber organ. Mr. Hopkins, on the other hand, prints two scales for
16-feet toned Bourdons, the larger of which gives 6-1/8 inches by 4-5/8
as the inside measurement of the CCC pipe; while the smaller gives 5
inches by 3-3/8 for the same pipe. We may safely adopt this larger
scale of Mr. Hopkins; and we will only say further that with our light
2-inch wind the mouths should be cut up one-third of the width, or
rather less, and the foot-holes should be of ample size.
[5] Rev. F. G. Hayne, Mus. Doc., "Hints on the Purchase of an Organ."
Novello, 1867.
2. Their location in the organ must depend very much on special
circumstances. When they can be placed in a row at the back of the
instrument, their connection with the pedals becomes very simple, two
sets of squares with trackers running under the bellows being all that
will be necessary. If the room has abundance of height, the back set of
squares may act on a roller-board, and then the pipes can be disposed
symmetrically, the largest at each end.
3. The board on which they stand will not require a slider. It will be,
in fact, a wind-chest only, a long box of stout pine or deal, having
holes in its top countersunk to receive the pipe-feet. Under each hole
is placed a pallet or valve, held up by a strong spring, and having a
pull-down wire passed through a brass plate in the usual way.
The aperture of the wind-trunk is in the lower board of this chest, and
over it, before the board is in place, is fitted a valve, faced with
leather, and made to slide to and fro between guides. An iron spindle,
turned to fit accurately in a brass collar, carries an arm jointed
to the valve by a connecting rod or trace; and outside the chest it
carries another arm, at right angles to this, jointed to the draw-stop
handle or its trace. We have, in fact, a trundle passing air-tight
through a collar, and by this simple contrivance we can shut off the
wind at pleasure from the chest. Other methods of effecting this are in
use, and may easily be devised. The pipes are very frequently placed
on both sides of the organ, to the right and left. In this case the
two chests will be at right angles to the manual chest or chests, and
the action will be less direct. But it will be readily arranged as
follows:--The pedal roller board will be long enough to act upon sets
of squares, carried on the organ-frame to the right and left of the
player, and at any convenient height. The other arms of these squares
act by trackers on roller-frames placed under the chests.
There are cases in which this roller-board will be better placed at
the back of the organ, the connection between it and the pedals being
by squares and trackers; and there are also cases in which a large
roller-frame lying upon the ground under the bellows may be made to
answer every purpose. Bell-cranks, or horizontal squares, may also
transmit the pressure of the foot on the pedal by other squares and
trackers to the pedal pallets in a manner analogous to that of the
draw-stop action, Fig. 49. There is abundant room for ingenuity and
contrivance in all these details; the essential points are strength,
quietness, and accessibility for repair or adjustment.
Some of our readers may be able to indulge in the luxury of a second
pedal stop. This should be a Violoncello in metal, of 8-feet tone
and length. In this case the pedal chest or chests will be regular
sound-boards, with sliders; or the Sub-bass may be on a chest as
already described, while the Violoncello may be on another, with two
actions.
We have only to add, that the power and effectiveness of small organs
may be increased by the contrivance called a "Terzo Mano" (Third
Hand), or octave coupler. Let us suppose that an ordinary action has
been fitted with backfalls in the usual positions. Then a second
bridge, rising and falling by a draw-stop, is introduced, carrying
skew backfalls which act on the pull-downs an octave higher than the
first set. Thus the key CC will take down the Tenor C note, and so on
throughout the scale. It is evident that the effect on the ear will
be nearly, though not quite, the same as if each 8-feet stop had its
corresponding 4-feet stop drawn with it. An Open Diapason will sound
like an Open Diapason and Principal; a Stopped Diapason, like a Stopped
Diapason and Stopped Flute, &c. To render the illusion complete, the
pipes should be carried up twelve notes higher than the apparent
compass of the key-board, that is to say, if the key-board has
fifty-four notes the sound-board should have sixty-six grooves.
In a similar way the pedal Sub-bass may be made to play in octaves,
producing the effect of a Sub-bass, 16-feet tone, with a Flute-bass of
8-feet tone added to it.
Of all such mechanical devices it must be said, finally, that neatness,
accuracy, and noiseless precision of action are the conditions
necessary to complete success.