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THE MUSIC TRADE REVIEW
13
Expression Control, Whether Obtained by Choker or Hammer-Rail Sys-
tems, Has Not Yet Reached Perfection in the Player-Piano—The Salient
Features and Essential Points, Good and Bad, of Both Methods Pointed Out.
It cannot be emphasized too often or too strong-
ly that the expression control of the player-piano
is merely a series of more or less effective com-
promises. To what extent these compromises ful-
fil the purposes for which they are proposed and
carried out can be decided only upon the merits
of each case. In all cases, however, the facts are
substantially the same, namely, that expression
control as at present worked out is a system of
compromise.
Dynamic control, with which the present article
proposes mainly to deal, falls naturally into two
divisions. The first has reference to the fact that
a single source of power is used for playing, and
that this power is produced by the bellows system.
The second exists because it is necessary to find
ways and means for sub-dividing the distribution
of this power so as to permit of dynamic contrast
in playing. Upon the existence of the latter con-
dition depends all the peculiar compromises which
we are now called on to investigate.
The Fundamental Idea in Power Distribution.
There are several ways in which the power pro-
duced by operation of the bellows system may be
distributed, but all of them rest on the same fun-
damental idea, That idea may be concisely de-
scribed as the "tension switch." In other words,
means are provided whereby, through the depres-
sion of a button, the moving of a lever or the un-
covering of a port in the tracker-bar by registration
with a special perforation in the music roll, the
power at the pneumatic stack may be reduced to a
given fixed level, usually considerably lower than
the normal level of normal pumping power. This
artificially induced "soft expression," as it is
rather inaccurately called, may be cut out by re-
verse manipulation of the controlling means, so
that if these be handled rightly there may be made
as many changes from the fixed soft level to the
level at which the pumping is producing power at
any moment as are necessary or desired.
This system is, of course, a system of com-
promise. It is plain that there can be but one
excuse for it, namely, facility in obtaining sudden
contrasts for accentuation. Long continued level
of one power, succeeded by a continued level of
another power, represents the general state of the
dynamic treatment of a complete piece, but such
conditions can best be brought about through pedal
technique. The choker system, whereby an arti-
ficial fixed level of low power is induced, operates
best when used momentarily in obtaining dynamic
contrast for accent.
Now it is at once evident that this latter system
has a serious defect in the fact that it works all
over the range of the piano and is not susceptible
of selective control. Hence, seeing that there is
always roughly a' sort of division between the ac-
companiment and the melody in a piece of music,
some sort of physical division must be made in the
note range in order roughly to accommodate this
condition, since it is evident that in general terms
the accompaniment and the melody must be played
a + different dynamic levels. Hence it is customary
to divide the pneumatic stack into two divisions,
each equipped with a separate governing device
for producing low tension playing. A division into
three or four sections, with corresponding gov-
ernors, would undoubtedly be still better, but the
trade has not yet perceived the necessity for this,
which is a pity.
The Simplicity of the Governor System.
The governor system is simple. It consists mere-
ly of an automatic cut-off. The air from the
pneumatic stack is compelled to pass, on its way to
the bellows, through a box containing a movable
wall, which is held up by means of an expansion
spring. Attached to the inside of this moving wall
is a connection of some kind with a sliding valve
which partly closes the opening nearest the bellows,
the proportionate size of the opening being thus
dependent on the position of the slide, which in
turn depends on the position of the moving wall.
When the pumping begins the air pressure in the
box is reduced, as it is in the bellows, and the
further it is reduced the more will the atmospheric
pressure tend to push in the moving wall, pro-
vided the latter is held open by a spring not too
powerful to be overcome by this pressure. In
point of fact, of course, the spring exerts on each
square inch of superficies of the moving wall only
a few ounces pressure, often not more than two
ounces. Hence, as soon as pumping begins, the
moving wall partly shuts down and the slide con-
nected with it is moved over the air passage, partly
closing it and so shutting off the flow of air from
the pneumatic stack to the bellows. The degree of
power depends on the proportionate dilution of the
air in the pneumatic stack, which in turn depends
upon the rate of outward flow. This depends on
the size of the passageway. Hence, if the spring be
set to give a pressure outwards on the moving wall
of, say, two ounces, any power exceeding this will
push in the wall and cut off the passage, so that the
playing power will always be equivalent to this two
ounces per square inch pressure on the pneumatic
as long as the air must pass through the controlled
passageway. If, however, another passage be
opened, so that the air need not pass through the
controlled way, then the playing power will be
equivalent to any rate of pumping existing at any
given moment, will, in fact, be uncontrolled by the
choker.
If the direction of flow of the air be thus con-
trollable at will, it is evident that a change from
fixed low level to any higher level one can get by
any rate of pumping desirable may be had very
quickly. That, in effect, is the choker system.
The hammer-rail system is different. In this
case pneumatic or direct lever means are provided
whereby the hammer rail, divided into two, three
or more sections, may be moved, section by section
or as a whole, towards the strings, whereby the
blow of the affected hammers may be shortened
and their sounds thereby diminished in intensity.
The difference between the two systems lies prin-
cipally in this, that the first goes to a fixed level,
rot affected by change in pumping, since hard
pumping on the choker system will simply collapse
the moving wall still further and cause it to cut
off the air passage still more; while the second,
which causes the hammer blow in selected parts
of the range to be diminished in effectiveness, also
permits a further modification through manipula-
tion of the pedals and consequent change in vacuum
power. A hammer, even when close to the string,
responds under a hard blow more rapidly than
under one softer.
Both Systems Have Defects.
Both systems, of course, represent compromises
with the conditions existing, and both are more or
less defective. When used in combination, that is
to say, when a hammer-rail division is used in
connection with a single choker for the entire
range, it is probable that on the whole one may
work somewhat more delicately, but it cannot be
said that the results are good enough to justify any
special excitement. However, it will be advisable
to have a clear idea of the comparative merits of
the two forms.
The choker system enables changes from low
to high tension to be made more quickly than is
possible with the pedals alone. Hence, it is a
quicker accent maker.
The choker system, however, has the disadvan-
tage that the low level is fixed, and therefore pre-
sents an unvarying monotony of color when in
use, a decided obstacle to the musical efficiency of
the instrument.
The hammer-rail system gives contrast and per-
mits the soft level to be varied. Hence, it has in
this respect a great advantage.
The hammer-rail system, however, has no accent-
ing power of itself and is entirely negative in its
nature. Hence it provides only an auxiliary to
the pedals without improving the accentive ca-
pacity thereof.
Players of the sensitive single valve type usually
have the hammer-rail system, while those of the
large reserve double valve type more often have
the choker'system. Sometimes, of course, the two
are combined. In grand pianos it is not practical
to use hammer-rail control, and therefore the
choker system is the only one available.
It is well that the peculiarities of the two sys-
tems should be understood and that there should
be no confusion of thought regarding them. To
remove any such confusion has been the purpose
of this article.
AUTOMATIC GRAND IMPROVEMENT.
(Special to The Review.)
WASHINGTON, D. C, January 24.—William J.
Keeley, of New York, was last week granted Pat-
ent No. l,lf)8,645 for an automatic grand piano,
which he has signed to the Auto Pneumatic Action
Co., same place, the object of which is to improve
the arrangements and constructions used in auto-,
matic grand pianos, and the invention particularly
relates to an improved arrangement for the op-
erating pedals and motor.
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Sole Distributor
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417 FIFTH AVENUE, NEW YORK
M s
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WO*CEST», MASS.