TUNING.
Having described the improvements in pipes, we now consider how they
are tuned, and the first thing we must notice is the introduction of
equal temperament.
About fifty years ago most organs were so tuned that the player had to
limit himself to certain key signatures if his music was to sound at
all pleasant. Using excessive modulation or wandering into forbidden
keys resulted in his striking some discordant interval, known as the
"wolf." The writer remembers being present at a rehearsal of Handel's
"Messiah" in St. George's Hall, Liverpool, Eng., in 1866, when the
organ was tuned on the unequal temperament system, and there was a
spirited discussion between the conductor and Mr. W. T. Best, who
wanted the orchestra to play "Every Valley" in the key of E flat so as
to be in better tune with the organ.
The modern keyboard is imperfect. One black key is made to serve, for
instance, for D sharp and for E flat, whereas the two notes are in
reality not identical.[1] To secure correct tuning and tone intervals
throughout, forty-eight keys per octave are required, instead of the
twelve now made to suffice.
In what is called the _equal temperament_ system the attempt is made to
divide the octave into twelve equal parts or semi-tones, thus rendering
all keys alike. To do this it is necessary to slightly flatten all the
fifths and sharpen the major thirds. The difference from just
intonation is about one-fiftieth of a semi-tone. Although recommended
and used by J. S. Bach, equal temperament was not introduced into
English organs until 1852.
Much has been lost by adopting equal temperament, but more has been
gained. To a sensitive ear, the sharp thirds and fourths, the flat
fifths and other discordant intervals of our modern keyed instrument,
are a constant source of pain; but the average organist has become so
accustomed to the defect that he actually fails to notice it!
The change to equal temperament has on the other hand greatly increased
the scope of the organ and has rendered possible the performance of all
compositions and transcriptions regardless of key or modulation.
The tuning of an organ is seriously affected by the temperature of the
surrounding air. Increased heat causes the air in the open pipes to
expand and sound sharp contrasted with the stopped pipes through which
the air cannot so freely circulate. The reeds are affected
differently, the expansion of their tongues by heat causing them to
flatten sufficiently to counteract the sharpening named above. Hence
the importance of an equable temperature and the free circulation of
air through swell-boxes, as described on page 59, _ante_.
NEW METHOD OF REED TUNING.
Organ reed pipes, especially those of more delicate tone, fail to stand
well in tune, especially when the tuner is in a hurry or when he does
not know enough of his business to take the spring out of the reed wire
after the note has been brought into tune.
Few persons fully understand the reason why reeds fail to stand in tune
as they ought to.
[Illustration: Figs. 31-35. New Method of Tuning Reeds]
Figures 31, 32, and 33 will serve to make clear the chief cause for
reeds going out of tune. Figure 31 may be taken to represent a reed
block, eschallot, tongue and tuning wire at rest.
In this case the tuning wire will be pressing firmly against the tongue
at the point B, but said tuning wire will not be subjected to any
abnormal strain.
Turning to Figure 32, if we use the reed knife and slightly lift the
tuning wire at the point C, friction against the tongue at the point B
will prevent said point B from moving upward. (In this connection it
must be borne in mind that the co-efficient of friction in repose is
much greater than the co-efficient of friction in motion.)
In consequence of the drawing up of the tuning wire at point C, and the
frictional resistance at point B holding the latter steady, the lower
part of the tuning wire will assume the shape shown in Figure 32, and
point A will in consequence move farther away from the tongue.
Now, if the reeds be left in this state and the organ be used for any
length of time, it will be found that point B of the tuning wire will
have risen upward until the abnormal strain upon the tuning-wire spring
has been satisfied. In consequence of this, this particular note will
be sounding flatter in pitch than it ought to do.
Conversely, if the portion of the tuning wire lettered C be slightly
driven down, as in Figure 33, the retarding effect of the friction of
repose at point B will cause the lower portion of the tuning wire to
approach nearer the tongue than it should do.
If now this reed be left in this state, after the pipe has been used
for some time and the tongue has been vibrating, it will be found that
point B on this tuning wire will have traveled nearer to the tip of the
tongue, in order to relieve the abnormal strain upon the lower portion
of the tuning wire. Point A will then have resumed its normal position.
In Figures 32 and 33, the defective action of the lower portion of the
tuning spring has been purposely exaggerated in order to make the point
clear. This bending of the tuning wires, however, takes place to a
much larger extent than most organ builders imagine. It is the chief
reason why reeds fail to stand in tune.
When point A on the reed tuning wires is rigidly supported and held by
force in its normal position, reeds can be made to stand in tune almost
as well as flue pipes.
Figure 34 represents the Hope-Jones method of supporting the tuning
wire at point A. It consists of having a brass tube T inserted in the
block moulds before the block is cast. This tube T therefore becoming
an integral part of the block itself. The inside bore of tube T is of
such diameter that the tuning wire fits snugly therein.
In Figure 35 another method used by him for accomplishing the same
purpose is shown. In this case a lug L is cast upon the block,
forming, indeed, a portion of said block. The lower end of lug L is
formed into a V, which partly embraces a tuning wire and supports it in
such manner as to prevent improper movement of said tuning wire at
point A.
When this method of construction is employed, the reeds are very much
easier to tune, and, when once tuned, will stand infinitely better than
reeds made in the ordinary way.
[1] Some organs have been made (notably that in Temple Church, London)
with separate keys for the flats and sharps.