An Improved Sound Generating, Augmenting, and Sustaining Device for Pianofortes and other Musical Instruments with Metallic Strings.
Year: 1889

page_text: Date of Application, 27th June, 1889-Accepted, 22nd Mar., 1890
COMPLETE SPECIFICATION.
An Improved Sound Generating, Augmenting, and Sustaining
Device for Pianofortes and other Musical Instruments with
Metallic Strings.
I Dr. RICHARD EISENMANN of Berlin N. Prussia Great Hambourg Street 18/19
do hereby declare the nature of this invention and in what manner the same is to be
performed, to be particularly described and ascertained in and by the following
statement:
The intensity of the sound, generated by the striking of the hammer against the
strings of a piano diminishes immediately after the stroke.
To retain the sound in its original strength, even to increase it, the undulatory
movement of the strings is sustained by electromagnets, the current of which is
regulated by microphones in the following manner:
The electromagnets E E are fixed on a lath Le over or under the strings-(SS).
The one end of the wire of all electromagnets is conducted to the pole (K) of an
electric battery or any other electric source. The other end of the wire of each
electromagnet is conducted to a spring, against which another spring is pressed, when
the corresponding key is pressed. For grand pianos it is more convenient to fix the
two metal springs F, F, on a wooden lath L, over the dampers (D). The two
springs are joined by a metallic elongation (C) of the dampers, when the dampers are
raised by the keys. In this case the cominion pedal must be arranged so," that it
cannot raise the dampers as high, as the keys do.
1
From the spring F, a wire is conducted to a microphone. The microphone can be
fixed on the sound board of the piano or any where else near the instrument or on
it. In the drawing R R is the sound board of the piano. At the point U a spring
with a platina point I is fixed. At H a piece of carbon is screwed on. The point I
also may be of carbon. It also would be sufficient for one part only of the microphone
Instead of the microphone thus described any other
to be fixed to the sound board.
microphone may be used.
From U a wire leads to an extra pedal P.
This pedal in the first place causes the lath L, with the electromagnets to approach
the strings.
The nearer the electromagnets are, the greater is the intensity of the attraction and
consequently of the sound-inversely proportional to the square of the distance. The
pedal is also connected to the pole of the electric battery by several coils of
wire (B, B B). Under the pedal as many metal springs (1, 2, 3) are fixed each
isolated from the other, but each connected with a corresponding coil.
When the pedal is pressed down, the electric current flows through the metal
springs, avoiding the coils. The connexion of the pedal with the pole L can be
arranged so, that, the more the pedal is pressed down, the deeper the electrodes dip
into the fluid of the battery. It also can be arranged so, that the more the pedal is
pressed down, the more electric piles are brought into action. In this manner, the
nore the pedal is pressed down, the greater is the intensity of the current. When
the key and the pedal are pressed down, a current flows from the one pole K through
the electromagnet E E over the two springs F, & F, to the carbon plate H passes the
platina point I, the spring F U and flows from there over the pedal P to the pole L.
The string beginning to vibrate, the sound-board vibrates accordingly and with the
sound board the platina point I against the carbon plate H.
In this manner a
egulation of the current exactly synchronic with the vibration of the strings is
effected and consequently the maximum of the attracting effect of the electromagnets.
On a good sound-board a single microphone is sufficient to regulate all the electro-
magnets. Notwithstanding the use of several is advisable, because certain parts of

page_text: the sound board answer certain tones better, than others. The strength of the current
in an electromagnet would be altered, if instead of a single note a whole chord was
struck. To avoid any alteration, a coil W of the same resistance, as the electromagnet
EE is inserted, so that, when the pedal alone is pressed down, a current flows from
the pole K of the battery through the coil W over the springs F, & F, and the pedal
to the pole L. If the pedal and one or several keys are touched, the current
instead of passing through the coils, W passes there corresponding electromagnets, so
that no alteration of the resistance takes place.
The use of microphones allows of the employment of inductive currents. Therefore
one may use magnets with inductive coils instead of the electromagnets with the
primary intermittent or undulatory current.
As the electromagnets alone are sufficient, to put the strings into vibration, the
hammer and with the hammer the whole mechanism belonging to the hammer may
be omitted. In this manner the electromagnetic mechanism thus described may be
employed on any musical instrument with metallic strings which can be attracted by
electromagnets.
The clangtint or timbre of the sound, that means, the quality, through which
we recognize the same tone-for instance A on different instruments, depends on
the harmonies or overtones, which accompany the principal tone. The sounding of
the overtones depends on the place at which the shock is imparted to the string,
therefore the clangtint of the sound changes accordingly to the spot, where the
attraction of the electromagnets takes place. So the imitation of other instruments
is effected by placing the lath. with the electromagnets on different parts of the
strings, for instance the imitation of a violoncello is acquired by placing, the lath
with-the-electromagnets-over-the-middle of the strings.. In this case one single
attraction is sufficient and no intermittent current is wanted.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, declare that what I
claim is
1. An electromagnetic mechanism for pianofortes and other musical instruments
with metallic strings to generate sustain and augment the sound effecting vibrations
of the strings by the attraction of electromagnets or magnets with inductive coils,
the current of which is regulated in accordance with these vibrations by microphones
as described.
II. The peculiar application of the dampers of grand pianos to close the current
of the electromagnets, as described.
III. The imitation of other instruments, by putting the electromagnets on different
parts of the strings.
Dated this 17th of June 1880
DR. RICHARD EISENMANN,
Berlin, N. Prussia.