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TECHNICAL^SUPPLY DEPARTMENT
William BrmdWlnte,7ecAmcalEditor
Opposing Physical Views of Functions of
Hammer in the Production of Piano Tone
The Recent Work of Satyendra Ray, of Allahabad, India, and R. S. Clay, in the Dic-
tionary of Applied Physics, in Investigating the Hammer Blow
AM probably not the least sinner among
those who have taken time and space to
talk about the ever mysterious questions
which surround the processes of tone produc-
tion in the pianoforte. Perhaps some of the
time and some of the space have been wasted,
although I am not conscious of any gross errors
either in fact or in conclusion; at least of no
errors grosser than have been, and are being,
daily committed by other persons of equal or
greater authority.
The fact, of course, is that the whole subject
is obscure. The experimental method is very
difficult to apply and only of late can it be
.^aid that even approximate determinations
have been made. Nevertheless, although acous-
tical progress has, of late years, been very
slow, owing to the very small number of those
who take a practical experimental interest in
it, something is being done.
The Hammer Thesis
In some recent articles on this page, espe-
cially in one which was an extract from the
manuscript of a new book on pianoforte design
and construction now under way, I had some-
thing to say about the influence of the piano-
forte hammer in the production of musical
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sound from the pianoforte string. My general
thesis may be briefly stated. It is that, other
things remaining equal, the best hammer is that
which has been the most highly compressed
during the process of gluing up, so that it be-
comes as hard as possible. These hammers,
whether we consider the heavy ones in the bass
or the lighter ones in the treble, are then to be
treated by the tone-regulator with the needles
in such a manner as to produce a soft interior
cushion, while retaining the outer surface, where
the contact is made, as hard as possible. To
master the process of needling which is to ac-
complish this desideratum is, of course, a mat-
ter of technic, which can only be acquired by
careful and continued practice. On the other
hand, there is no reason why one should not be
able to devise a form of gang needle-holder,
which should enable the tone regulator mechani-
cally to make the necessary deep strokes into
the interior of the felt, while leaving the crown
of each hammer untouched, and at the same
time not spoiling the outer hard surface. As a
matter of fact, given a machine with the needles
properly spaced, and with the hammers brought
one by one into proper relation to it, the tone
regulator would be able to work not only more
rapidly but much more skilfully and accurately.
It might be objected that this use of a
needling machine tends to an unscientific uni-
formity and mechanical rigidity in the method
of treatment. But this is not so, for the tone
regulator, proceeding according to his knowl-
edge of the scale with which he is working, must
use his personal skill to assure himself when
each hammer has been properly worked.
I shall not, at this moment, go into any argu-
ment as to the methods of tone regulating from
beginning to end of the process. But I wish
to make some observations upon another point
of considerable importance.
Mr. Satyendra Ray
In a recent number of the Physical Review
(December, 1926), Satyendra Ray, of Allahabad
University, India, gives some results of his
work upon the vibration forms of pianoforte
strings. Among other things he shows ex-
perimentally that the best result in the way of
tone production is obtained when the time of
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contact of the hammer with the wire is equal to
the time of the free vibration period of the lat-
ter. In other words, when t/p = 1, the string
gives forth the strongest fundamental and also
has the second, third and fourth partials suffi-
ciently powerful to overcome the possibly dis-
agreeable effect of higher dissonant partials.
Interpreted in terms of piano manufacture,
this simply means that the string which gives
the sound C=261.6, for instance, will emit the
most agreeable sounds, as judged from the gen-
erally accepted ideas of piano makers and play-
ers, if and when the contact time of the ham-
mer against it is equal to .0039 sec.
Satyendra Ray also finds that almost iden-
tically good results are to be had when the
free period of vibration is just one half of that
of the hammer-contact time.
Now, I venTtlre to think that we have here
some confirmation of my thesis regarding the
hardness of the outer or contact surface of the
hammer, as against the soft inner cushion. For
it is evident that if the outer surface be highly
compressed, the reaction of the hammer will be
rapid, while on the other hand, if the inner
cushion be soft, the blow cannot smother the
fundamental under a crowd of dissonant partials,
simply because, although the displacement of the
wire by the hammer will begin rapidly, it will
at once be partially damped, after the funda-
mental has been properly established.
The Opposing Thesis
An opposite view to this, however, has been
put forward in the Dictionary of Applied Phys-
ics (London, 1923) by R. S. Clay, author of
the article Pianoforte, who argues that the best
tone quality will be evoked when the blow be-
gins gently and the displacement not there-
after damped. Pursuing this thesis, he argues
that the outer or contact surface ought to be
soft and the inner portions hard.
Yet if this were to be the general practice,
we should see two regulators "picking up" the
outer surfaces of hammers, just as tuners who
have less experience and understanding than
enthusiasm and ambition, are sometimes caught
doing. But the conclusions which have been
reached by the best tone regulators, after more
than a century of experiment, are more in ac-
cord with the hypothesis I have been urging.
This is not said by way of disrespect for the
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