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Патент USA US2403664

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July 9, 1946.
Filed Oct. 24, 1942
3 Sheets-Sheet l
if? £9»
July 9, 1946.
Filed Oct. 24, 1942
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3 Sheets-Sheet 2
95 /
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July 9, 1946.
_ 2,403,664 - >
'Eiled Oct. 24, 1942‘
, s'sneets-sheet 3
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Patented July 9, 1946
2,403,664 *
soLo ELECTRICAL MUSICAL ms'rammn'r - I
Nicholas Langer, NevhYork, N. Y., asaignor to
Central Commercial Company, Chicago. 111-, a
corporation of 111111011“?
a' ' Application October 24, 1942, Serial No. 463,291
9 Claims. (oasis-s28)
The present invention _ relates to electrical
musical instruments, and, more particularly, to
The invention also provides novel tone color
modifying circuits and devices capable of being.
an electrical musical instrument of the mono-'
adjusted to a ‘practically unlimited number of
distinctly different tone colors without requir
ing anylwcomplex electronic devices for the pur
phonic, or melody, type.
It is an object o! the present invention to
provide an electrical musical instrument of the
described type having a novel and improved
pose of phase shifting, distortion and the like -
effects now,v commonly used ior such purpose.
character and presenting substantial advantages
It is also within the contemplation of the
over conventional electrical musical instru
invention to'provide an electrical musical in
10 strument including a glow-discharge oscillator
It is another object of the present invention
of special type which is tree from the detrimental
to ‘provide an electrical musical instrument of
v e?ects of leakage and atmospheric variables and
the melody type, capable of producing a single
is capable to maintain its correct tuning for a -
musical sound at a time within a relatively wide
range of pitch and tonal quality.
It is a further object of the present invention
to provide an improved electrical musical in
strument oi the solo, or melody, type in which
a single oscillator tube of the gaseous discharge
relatively long time.
The invention also contemplates an electrical
musical instrument of the melody type, which
is extremely simple in constructlon'and gener
' ally includes only a single oscillator tube, pro
- vides excellent musical effects of a practically
type is adapted to-produce musical oscillations go unlimited variety, and whichv may be readily
over a musically useful range of several octaves
and having a large variety of tone colors or
timbres, without recurring to the heretofore
employed complex procedure of employing a plu
rality of octavely related cascaded oscillators.
Still another object of the invention is to pro
vide a monophonic electrical musical instrument
employing a single glow-discharge tube oscil
manufactured and sold on a practical and com
mercial scale at a low cost.
Other and further objects and advantages of
the present invention will become apparent from
thefollowing description taken'in conjunction
with the accompanying drawings, in which
Fig. 1 illustrates in a somewhat fragmentary
manner the circuit diagram of an electrical
later operatively associated with a keyboard or
musical instrument embodying the principles of
playing manual of relatively restricted range and so the present invention.
adapted to control the pitch of the oscillations
Fig. ,2 depicts the circuit of a preferred form
produced within a considerably greater musical
of tone filter system employed in connection with
Still another object of the present invention
‘is to provide an electrical musical‘ instrument 86
originally producing electrical ‘oscillations of ‘
very. complex waveform which may be readily
converted into musically useful and valuable
oscillations of a great variety of tone colors,
simulating the tone colors of most of the 40
orchestral instruments and in addition to this
also capable of producing many additional tone
colors or an altogether novel character not now
found in conventional musical instruments, or
in the stops of conventional organs.
Moreoventhe invention provides means and
the electrical musical instrument illustrated in
Fig. 1: and
Fig. 3 shows the circuit‘ diagram of a universal
tone ?lter system which in combination with
an oscillation generator producing oscillations
0! complex wave form is capable of producing a
practically endless variety of different tone colors.
The invention will be best understood from
description 01'. a preferred embodiment thereof
reference being had to Fig. 1 0! the drawings.
In order to facilitate understanding of the in
vention such elements which are of a more or
less conventional character and are well known
to those skilled in the art, such as the source
ins'trumentalities for producing additional tonal‘ of current, or power pack, the ampli?er and vol
effects, ‘ particularly tremolo effects. and per- " ume control, have been either omitted, or have
cussion type e?ects resembling those of plucked
strings by inertialess or electronic means in the 8.0
‘absence of mechanical interrupter-s. and similar '
{conventional devices.
been only diagrammatically shown.
Generallyv speaking, 'the ‘electrical musical '
instrument of the invention comprises a main
oscillator section.- a range control section, a
put section.
l0 . . . 2911, one contact 0! which is connected
tremolo-banjo section and a tone control or out
through a balancing resistance 40 to the sliding
contact of one of the potentiometers i! of group
H and then through common lead it of such
group to ground. Thus, it will be noted that
upon closing of any one of key switches 35 to
39, etc., a predetermined number of the serially
connected resistances 30 to Mn will be connected
Main oscillator section
The main oscillator section essentially com
prises an oscillator tube or the gaseous dis
charge type which is operatively associated with ,
a source of direct current voltage and with a
plurality of tuning elements, such as conden
across condenser 29 through one of balancing
sers and resistors 0! determined value to pro
10 resistances l0 and through one of potentiometers
duce electrical oscillations the frequency of
which may be varied in steps within a wide
1!. Selection of the proper value for resistances
iii to 3411. permits approximate tuning of the re
spective note, while displacement of the slider
on the corresponding potentiometer [5 will per
Referring now more particularly to Fig. l of
the drawings, reference character l0 denotes a 15 mit to individually adjust the operating voltage
effective upon depression of said key and thereby
source or direct current of suitable voltage which
to accurately adjust the pitch for that note. In
in practice is a power pack converting the alter
nating current taken from the electric mains into - this connection it may be pointed out at this time
that the value of resistances 31 to 3411, balancing
?ltered direct current oi substantially stable
voltage. In most cases this power pack may be 20 resistances l0 and individual tuning potentiome
ters iii are of a di?erent order. For example.
in common with that of the amplifier in view of
when main tuning resistor 30 is or about 1,500,000
the iact that the total current consumption or
ohms, resistance 3| to 3411. may be of progressive
the instrument is relatively low. Between the
ly increasing values from about 70,000 to about
positive and the negative terminals or this source
oi direct current is connected a voltage divider 25 500,000 ohms, balancing resistors 40 may have a
resistance oi about 25,000 ohms each and incl
resistance II from which various operating volt
ages may be taken of! for the di?erent sections of
vidual tuning potentiometers 15 may have a re
sistance of 5,000 ohms each. The object of such
the instrument, this resistance being connected
coordination of resistance values will appear as
in series through lead wire l2, and switch I 3 to
a group II of individual tuning potentiometers 30 the description proceeds.
comprising a number of small potentiometers l5
Range control section
connected in parallel, the other end of said group
being connected to ground through lead wire i8.
Generally speaking, it is not advisable to pro
Voltage divider resistance H is provided with
vide a single range greater than about 3 octaves
sliders I’! and It to take off voltages of desired 35 for various practical reasons. First or all, the
value, as it will appear more fully hereinafter;
extension of a single range obviously determines
and its total resistance’ is so adjusted thatthe
voltage drop across each of the tuning potenti
ometers I5 is about 4 to 6 volts. Condensers i9,
the number of switches and thereby the length of
the playing manual. In addition, as the total
the movable arm of thispotentiometer are con
quencies, such as soprano, alto, tenor or i, , Ht.“
resistance of the resistance chain II to 3011 in
20, 2| and 22 are connected across the various 40 creases with increasing range, if the range is un
taps of voltage divider resistant": ii and ground
necessarily extended, the relation between the
in order ‘to reduce the alternating current re
value of resistances in the circuit and the permis
sistance of the system to a relatively low value.
sible leakage becomes unfavorable and a?fects the
Between the two taps l1 and i8 of voltage‘di
permanency or stability of tuning. A range oi 3
vider II is connected main pitch control potenti 45 octaves is in most cases sufficient for playing any
ometer 23 which serves to adjust the operating
melody with the accompaniment of another in
voltage of the oscillator tube and thereby con- ‘
strument, such as a piano. In order to permit
trols the general pitch of the instrument. With
operation within various ranges of tone ire-i
nected in series tremolo coupling resistor 24, 50 ranges, it is preferred to shift the range oi‘ the
pitch balancing resistor 25 and output resistor
26, together with glow-discharge tube 21, range
control switch 20, tuning condenser 29, the latter
being connected to the negative terminal or the
source or current ‘l0. While any glow-discharge
tube oi good make and 0! stable characteristics
may be used, I iound that a glow-discharge tube
oi type VR‘75/30 provides excellent results.
To the common terminal of tube 21 and con
denser 28 is connected 0. chain of ?xed resistors
which comprises serially connected resistances
00, ii, 32, l3, l4 . . . “11. These resistances cor
respond in number to the number or notes of
different pitch which may be produced in a sin
gle range of instrument. Thus, for example, for
an instrument having a range or three octaves
from C to C, 31 resistances ‘are used and their
oscillator as a whole by one or more octaves.
the circuit of Fig. 1 two such ranges are shown.
it being understood that, of course, three or more
diiiferent ranges may be incorporated into the
instrument, if desired.
Range shifting is accomplished by means oi
range shifting switches l3 and 28 which are pret
erably combined into a single unit or the double
pole, double throw type, so that these two switch
ing operations are simultaneoushr performed. 0!
these switches, 28 switches tube 21 over into se
- ries connection with condenser II from con
denser 29. The relationship between the cap“
ities of 28 and 41 substantially determines the
frequency difference between the two ranses.
Thus, for example, if condenser 44 has a capac
ity twice as great as that of 28, the pitch of the
instrument will be lowered by an octave, ii con
resistance is so determined that upon connecting
a selected serially connected plurality thereof
across tuning condenser 28, the oscillator will be 70 denser ll has a capacity four times as great as
approximately tuned to notes or successively de
creasing pitch in correspondence with successive
notes or the tempered scale. Between the com
mon terminal or any two adjoining resistances
that of 2a, the pitch or the instrument will be
lowered by two octaves. While the range-chans
ing effect of the capacity in the oscillator circuit
is more or less equal for all 01 the frequencies
there is connected a switching key SI, II, 21, ‘I, 15 corresponding to actuation oi’ the‘verious key
switches, certain slight differences frequently oc
cur due to the di?erent impedance of the other
portions of the circuit at widely different Ire- ,
quency ranges. Therefore, to obtain and to
maintain musically perfect and correct pitch for
may have a resistance or 1.5 million ohms up to
10 million ohms, and more, according to the key
ing switch actuated. This proportion of the re
sistances is of considerable importance in assur
ing that upon actuation of several switching
keys at the same time always the higher note will
sound, as it will be explained more fully when
the operation of the instrument will be described.
ily observed that in the ?rst or "high range” po- ,
Tremolo and bomb sections
sition of the instrument, this second‘ group of 10
tuning potentiometers is not energized, one of its
The main oscillator section and the range
the several ranges, it is desirable to also provide
a second group 42 of individual tuning potenti
ometers 43 for the second range. It will be read-‘
bus ‘bars being disconnected at switch VI 3. , In the
shifting section in proper-cooperation are capa
second or “low range,” however, group 42' will'be
ble of producing a single sustained note of com
energized and group I 4 will be disconnected from
plex wave form over a range of several octaves,
the voltage divider resistance II. In this case de 15 such as, for example, three octaves, this range
pression of any one of switching keys will connect ,
being shiftable by 1 or 2 octaves up or down by -
a controlling potential to the oscillator tube de
actuating the range-shifting means described in
termined by the setting of the corresponding po
the foregoing. It has been found desirable to in
tentiometer of group 42, This potential is de
corporate means for producing a tremolo, that
livered to the tube through the resistance chain 20 is: to cause slight periodic changes in the pitch
30 to 3m and through a balancing resistance 44
of the oscillations produced, such periodic
which corresponds in function and in value to the
changes having a relatively slow rate such as
balancing resistors 40 connected between the
about 6 or 7 times a second. Such' periodic
keying switches and the sliding contacts of po
changes in pitch provide a musically valuable re
tentiometer group H.
25 sult similar to the well-known vibrato e?ect of
The objectof the provision of the balancing re
the string instruments and of the singing voice.
sistors 40 and H, one set for each group of tun
In accordance with the principles of the pres
ing potentiometers, is to substantially eliminate
ent invention, the tremolo e?ect is obtained by
the effect of the setting of the unenergized group
means of an auxiliary glow-discharge tube oscil
of potentiometers upon the energized group oi po-. 30 lator tuned to a very low frequency, such as 6 or '1
tentiometers. As it will readily appear from Fig.
oscillations per second. This tremolo oscillator
1, each switching key is at all times connected to
is so coupled with the main oscillator circuit that
the sliding contact of two potentiometers, one in
every time when the tremolo oscillator draws
each group, through a balancing resistance._ As
current from the common source, the available
suming that, for example, group H of- the poten 35 operating voltage for the main oscillator is some
tiometers is energized, a predetermined potential,
what decreased. Decreasing operating voltage
generally different from ground potential is ap- - '
causes decreasing frequency of the main oscil
plied to the switching key in accordance with the
> lator.
setting of the respective potentiometer. At the
In Fig. 1, reference character 4‘! denotes the
same time, however, a portion of this potentiom 40 tremolo tube, which preferably is a glow-dis
eter is shunted by a secondary current path com
charge tube having two cold electrodes. One ter
prising the two balancing resistors l0 and 44 in
minal of this tube is connected to' the common
series, lower bus bar 45 of group it and lower bus ' point of pitch-balancing resistor 25 and‘ output
bar 46 of group 42, the slider of a potentiometer
resistor 26, the other terminal of the tube being
43 in group 42 and a portion of said potentiom 45 connected through a ?xed resistance 48 of about
eter. Due to the fact however, that the balanc
1,500,000 ohms and an adjustable resistance 49
ing resistances have a considerably higher resist
of about 2,000,000 ohms to ground Two con
ance than the potentiometers, the effect oi’ this
densers 50 and SI of about 0.15 and 0.1 micro
by-passlng resistance on the setting of the ener
farad capacity, respectively, have one of their
gized potentiometer will be negligible. Thus, for 50 terminals connected to the common terminal of
example, if the individual potentiometers have a
tube 41 and resistance 48, their other terminals .
resistance of 5,000 ohms each and the balancing ‘ being respectively connected to two arms 52, '53
of a three-pole three-position switch 55. The
resistances have a resistanceof 25,000 ohms each,
the by-passing resistance will be in excess of
third arm, 54,0f switch 55 is connected across
, 50,000 ohms, while the portion of the potentiom 55 pitch-balancing resistor 25 and is capable of
eter across which such resistance is connected is
shorting the same in the third position 01' the
generally considerably less than.5,000 ohms so
switch through lead wires 56 and 51. It will be
that the setting of the energized potentiometer
noted that in the first position of the switch.
l5 will be the governing factor whereas the set
as illustrated in Fig. 1, arm 52 of the switch will
ting of the other potentiometer in the second 60 connect condenser‘!!! across tube 41 while the
group will be of practically no effect.
This ar
rangement is of considerable importance and
value because otherwise it would be necessary to
provide a complicated and bulky multiple switch
arrangement capable of switching over as many
as 37 key contacts from one group of potentiom
eters to the other. It is also worth noting that
the total resistance of the current path between
the lower terminal of any one switching key to
other two arms of the switch are inoperative. In
this position slow oscillations will be produced
by tube El and the tube will be lighted and ex
tinguished about 6 or 7 times per second. Every
time the tube is lighted, in addition tc the current
?owing to themain oscillator, vadditional current
will be drawn through resistors 24 and 2B, and
the voltage'drop across these resistors will slight;
ly decreasegthe frequency of the main oscillator
ground through the respective balancing resistor 70 at the same rate as the tremolo oscillator is oscll=
and tuning potentiometer is quite low with re
lating. The speed of the tremolo is determined
spect to the resistance of the resistance chain 30 '
by the value or elements 50, it and t9, and may
to 3412. at that point. Generally ‘speaking, the
be approximately adjusted by proper selection of
former resistance» is only slightly in excess of
50 and accurately adjusted by the adjustment oir
about 25,000 ohms whereas the resistance chain 75 resistance 6..
When switch 55 is placed into its third posi
tion, arm 52 will be inoperative, arm 53 will con
nect condenser 5| across resistors 48' and ‘9 and
arm Bl will short-circuit pitch-balancing resistor
2!. Connection of condenser 5| across resistors
ll and. 48 will likewise cause oscillations of ‘trem
olo tube 01, but the wave form will be greatly
di?erent. While the tube with a condenser across
the same produces a wave form characterized by .
6| having a value of about 25,000 ohms. One end
of the secondary winding ii of transformer II
is connected to ground through shield 82 while
the other through a lead 83 shielded by means
of shield 82 is introduced into the tone control
device generally denoted by reference character
64. A second decoupling resistance B5 of about
25,000 ohms is preferably connected in series
with this lead to prevent changes in the out
slow charge and rapid discharge of the condenser 10 put impedance being reflected back into the
main oscillator circuit and thereby causing slight
through the tube, connection of the condenser
pitch variations.
across the resistance will produce almost instan
The tone control device has the object of con
taneous charging of the condenser through the
verting the oscillations originally produced by the
tube and gradual discharge of the condenser
through the resistance across the same. The lat 15 oscillator and generally having an extremely com
plex saw-tooth wave shape into other oscillations
ter arrangement gives a wave form with very
of diiferent wave form by filtering out some of
abrupt peaks which superimposed upon the main
the harmonics and by reinforcing others. The
oscillator by means of tremolo or coupling re
tone control device essentially comprises a plu
sistor 24 causes such modulation of the main
oscillation which closely simulates the sound of 20 rality ‘of switches such as for example eight
switches of the push button type which can be
a string, plucked or struck in rapid succession.
actuated individually or in any desired combina
In the following, this effect, which is very at
tion of two or more switches at a time. By
tractive musically, is referred to as "banjo effect.”
actuating these switches, ?lter systems I to I
In view of the fact that generally faster oscil
lations, about 10 to 12 per second are required 25 may be selectively connected in series with the
outgoing signal, passing through some of the
for this banjo effect, condenser 5! has a lower
oscillations in modified form and grounding
capacity than condenser 50 to take care of the
other portions of harmonics of the oscillations
difference of speed between the tremolo and banjo
through a lead wire 88.
Experience has shown that in general the 30 ‘ While the general principles governing the fre
quency response of various ?lter circuits compris
tremolo oscillator has a slight effect upon the
ing capacitors, inductances and resistors in vari
general pitch of the main oscillator. More par
ous combinations are known, the theoretical de
ticularly, switching over from tremolo to banjo
termination of ?lter systems to obtain a certain
would slightly raise the general pitch of the main
oscillator. To compensate for this undesirable 35 musical result is so involved and uncertain in the
final result that experiment has been found the
change, is the object of the provision of pitch
simplest and quickest way to decide the type and
balancing resistor 25 which is in series with both
the value of the electrical elements for obtaining
the tremolo and the main oscillator tube. Short
a wave form simulating a_ determined musical tone
ing out of this resistor of about 15,000 ohms si
co or.
multaneously with switching over from tremolo
to banjo effect will lower the pitch of the main
I have found that excellent results are obtained
by means of small transformers employed as in
oscillator by the same amount as it would be
raised by the different impedance of the auxiliary
ductances in filter circuits with or without com
bination with other elements such as condensers
oscillator in the banjo connection. In this man
and resistances. ‘Transformers of the type used
ner, the pitch will be maintained constant re
in ampli?ers as interstage coupling transformers
gardless of whether the tremolo or the banjo ef
are. especially advantageous because they are
feet is used.
‘ In the middle position of switch 55 all three
arms thereof are inoperative. This is the neutral
readily obtainable on the market with a great
variety of winding ratios and taps and also be
position in which the auxiliary oscillator does 50 cause they are relatively small and inexpensive.
A single transformer may be used to selectively
not produce any oscillations. It is worth noting
provide a plurality of widely different induct
that tube 41 is‘ continuously lit in this case, its
ances according to whether the primary winding,
circuit being completed from the positive ter
the secondary winding, or only a portion thereof
minal of the source of current i0 through re
sistors 24 and 25 and then through resistors 48 55 is used. I have also found that by unipolarly in- ,
troducing the signal into one of the windings
and 00 to ground. This is essential in order to
of the transformers and unipolarly withdrawing
‘avoid any change in the general pitch of the main
the signal from the other winding also provides
oscillator in the tremolo-off position.
novel and interesting ?ltering effects. A trans
Output and tone control section
60 former used in. such a manner corresponds to
an electrical filter of unique characteristics in
The output signal is taken off at a resistance
that the signal is transferred from one winding
II connected in series with the main oscillator
into the other by means of a combination of uni
circuit. Any change in the impedance of the
formly distributed capacitive and inductive cou
output circuit is likely to change the general pitch
of the oscillator. Therefore, to substantially 65 pling, which deforms the original wave pattern
in a manner unobtainable in any other way. It
elminate such changes, it is desirable to have the
is also possible to employ one winding of a trans
coupling between the oscillator proper and the
former as an inductance and to short circuit the
output circuit as loose as possible. This is accom
other winding either directly or through a highly.
plished by making the value of output resistance
20 relatively small with respect to the internal 70 resistance or small capacity whereby further mod
i?ed tone colors are obtained.
resistance of the oscillator circuit such ‘as, for
.The electrical circuits incorporated into the
example, 10,000 ohms. The signal corresponding
tone color section will be best understood from
to the voltage drop along resistance 26 is intro
Fig. 2 of the drawings. Reference character II
duced into the primary winding 58 of an output
transformer ll through a decoupling resistance 76 generally denotes a ?lter system which is capable
2,403,654 .
of producing three distinctly diil'erent tone col
ample, a small telephone coil of’ about 2000 ohms
resistance, with its usual iron core. At its out
put end, winding 98 is grounded through a capac
ity I02 of about 0.004 mf. This stop provides an
ors according to whether push button I, 2 or 5 is
actuated. The ?lter system comprises a small
transformer 80 of the type used as interstage
coupling in ampli?ers having a secondary wind
ing 95 with a greater number of turns than the
primary winding 86. One end of winding 85 is
excellent oboe in the high range and _a bassoon
in the low range.
Push button 5 has been already discussed in
connected to the upper terminal of a condenser
the foregoing. Push button 6 upon actuation will
81 of about 0.003 mf., of which the lower terminal
simultaneously close switches 11 and ‘I8 and there
is grounded, and to one contact of both switches 10 by connects one winding of a small transformer
‘I0 and' 68. The other end of said winding] of
I03 between the input and output signal bus bars
transformer 82 is connected to contact 89 of
99 and 94. This transformer is of very small
double—throw single-pole switch 89. The center
dimensions, such as are sometimes used in hear
.point 90 of this switch is connected to the upper
ing aids and has a primary to secondary ratio
' terminal of another condenser 9I of about 0.003 15 of about 1 to 10, and a direct current resistance
mf., likewise groundedat the other terminal, and
of about 45 ohms and 450 ohms, respectively. At
is also connected to one contact of both switches
the input end of the secondary or high resistance
89 and 61. The second‘ stationary contact 92 of
winding I04 there is a condenser I05 of about
switch 89 is connected to the center tap of wind
0.003 mi. and an inductance I06 connected to
ing 85 of transformer 84 and also to one contact 20 ground. The inductance is a conventional tele
of switch ‘I9 coordinated to push button unit 5
phone coil having a direct current resistance of
of which the other switch ‘I5, has one of its con
about 4000 ohms. The other winding of the trans- I
tacts connected to one end of the other wind
former 'I 03 is either left ?oating or may be shorted
ing of the transformer. ,
by means of'a high resistance I08 of the order of
This single‘ ?lter combination is capable of 25 about 50,000 ohms. This shorting lead of pre
producing three di?erent tone colors. Thus, upon
determined resistance introduces distortion into
actuating push button I, switch 61 and switch 99
the ?lter system, the amount of which can be '
accurately adjusted by the value of the resistance
are closed and switch 99 connects contacts 88 and
90. In this case the full winding 85 is'connected‘
whereby a very precise control upon the result
between input bus bar 93 and output bus bar 90 30 ing tone color is obtained. This ?lter gives a
tone color or stop known in the organ art as
and two condensers 81 and 9I are connected to
ground at either end of such inductance. The
musette in the high range and that of a sax horn
in the low range.
result will be a tone color corresponding to ?ute
in the high-pitch. range of the instrument and
Upon depression of stop button ‘I switches ‘I9
to French horn in the low-pitch range of the in 35 and 80 are simultaneously closed and a small
strument. Upon actuation of push button 2, both
transformer I09 having a primary winding I I0
switches 89 and ‘III are closed and only one half
and a secondary winding III is connected-inv
of the inductance will be connected between bus
such a'manner that the input bus bar 93 is con
bars 93 and 94, the same condensers being con
nected unipolarly to one end of the primary and
nected between the ends thereof and ground. 40 the output bus bar 94 is likewise unipolarly con
This produces a tone color corresponding to that
nected to the secondary winding at one end
of a soprano saxophone in the high-pitch ‘range
thereof. The transformer is of the same type
and to a bass clarinet in the low range. Upon
as the one used in ?lter 6. As it has been already
actuation of push button '5, switches ‘I5 and ‘I0 are
explained in the foregoing, a ?lter of this type
simultaneously closed and the signal will be in
has rather peculiar electrical characteristics in
troduced at the center tap of winding 85 of trans
that it corresponds to a uniformly distributed
former-8| and is withdrawn through lead 98 con
inductance and a uniformly distributed capacity
nected to one end of winding 90 of the trans
combined in a single electrical element. The
former. It will be noted that one end of winding
resulting tone color is a trumpet in the high
85 is ?oating, while the other end thereof is
range and a tenor saxophone in the low range.
grounded through condenser 81, and that the
other end of winding 88 is likewise ?oating. This
Stop button 8 simultaneously closes switches '
8| and 82 whereby a direct lead H2 is connected
?lter of rather unusual construction produces a
between the input and output signal bus bars,
muted trumpet quality in the high range and an
said lead being by-passed to ground through an
effect closely similar to vox humana in. the low 55 inductance H9. 7 This inductance is a small
telephone coil having 2000 ohms direct current
Depression of push button 3 simultaneously
'closes switches ‘II. and ‘I2, and connects a resist
resistance. The resulting tone color is corre-v
sponding to an organ stop commonly called
?ageolet, both in the high and low ranges.
ance 99 of about'50,000 ohms between bus bars
93 and 94, each end of said: resistance being 60 The foregoing tone effects may be either in-. '
grounded through a condenser 99 and 91 of about
dividually employed by actuating a single push
. 0.003 mf. This ?lter produces an excellent string
button, or stop, or two or even more stop push
quality corresponding to the tone color of a violin
in the high range and to that of a ’cello in the low »
Depression of push button- 4 simultaneously
buttons may be simultaneously closed. In the
latter case further interesting and pleasing tone
colors are obtained rather than a direct additive
effect of the individual stops. The following table
closes both switches ‘I8 and ‘Iii~ and thus connects, ' should give some idea as to the principal tone
one half of winding 98 of a small interstage audio
colors obtainable by the judicious application of
transformer 99 between bus bars 99 and 90. The
the foregoing stops. Whenever a number fol
other end of said winding is ?oating and so is the 70 lows the name of a tone color or instrument,
other winding I80, preferably the one with the
lower number or turns. At the input end of wind
ing 98 it is grounded through an inductance III
of relatively high. value and also of a relatively
this indicates that while the resulting quality
istslmilar to the instrument in question it is
slightly di?erent from another quality of the
same name obtainable by means of another com
75 bination of stops. This can take care of in»
dividual difference of judgment or preference
frequently found among different Imusicians.
1 .................... _-
High range
Low range
Flute _______________ _.
French horn.
Violin. ...... __
Soprano saxophone..._ Bass clarinet.
Sax horn.
Tenor saxophone.
Muted ‘cello.
Bassoon 2.
Bassoon 3.
E55555%.5.5.E5 5
.............. ._
Bassoon 4.
Viola d'amour ....... __
....... ._' ______ .-
ii and 7 .............. _-
Woo wind .......... __
6 and 8_._---.'_ _______ ._
Shepherd's pipe ..... _.
After the output of the instrument has been
appropriately'modifled by means of the tone
color filters, the output taken off at output bus
bar it is introduced into a volume control p0
adjusted by means of main tuning potentiometer
23. Thereafter, range switches l3 and 2B are
placed in the high range position and the tuning
of the individual notes is correctly and accur
ately adjusted by means of the individual tuning
potentiometers of group i4 and then the same
procedure is repeated for the low range by plac
ing range control switches i3 and 28 into the
low range position and by adjusting the in
dividual tuning potentiometers of group 42. If
at any time there is some discrepancy between
the exact octave relationship of the high and
low ranges, this can be readily corrected by
adjustment of range control condensers 29 or H,
15 which are preferably of the mica compression
type to facilitate ready and continuous adiust~
ment. It has been found that the instrument
is very stable in tuning and as a rule does not
require retuning for long intervals of time.
Attention is directed here to the advantages
provided by means of the main tuning potentl
ometer 23 which permits continuously adjusting
the general pitch of the instrument within the
range of a few notes, simultaneously for both
25 ranges and without affecting the relative pitch
of the various individual notes which will retain
theircorrect intervals determined by the equal
temperament. Thus, by means of this single con
trol element, the instrument can be readily and
30 instantaneously tuned to anyistandard pitch such
as the international or the concert pitch or to ‘
tentiometer ill of any appropriate taper and
any other instrument of constant tuning, such
from this it is introduced into an amplifier Ill
as a piano or organ, whatever its general pitch
of suitable output and ?nally into a sound pro
is. Moreover, the same feature of my instrument
ducing means III. In view of the fact ‘that
makes it a transposing instrument so that a
the amplifier may be of any suitable type and 35 melody written in a difficult key or tonality, such
does not form part of the present invention, it
as C# major, may be instantaneously transposed
has been merely diagrammatically indicated.
into another very simple key. Thus, for example,
Resistance‘l i'l connected directly across main
by shifting the general pitch half a note higher,
oscillator tube 21 has a very high value, gen 40 the operator may play a melody in C major and
erally in excess of 500 megohms, and may be up
it will sound in C# major. This is a very great
to 2000 megohms. This resistance has been
advantage not only for the operator having but
found extremely effective in eliminating the
limited musical knowledge or skill but also for the
variable elect of leakage on the permanency of
highly trained musician.
tuning. As it has been set forth in the fore~ 45
In playing the instrument little experience is
going. certain portions of the circuit are very
required due to the fact that the playing manual
sensitive to leakage in view of the fact that some
controlling switching keys I! to 351: is closely
“of the current-carrying portions of the circuit
similar to a conventional piano keyboard with
themselves have a very high resistance, such as
which most people are familiar. In view of the
the resistance chain It to lln which'might have 50 fact that only one note is produced at a time, the
a value of up to 10 to 15 megohms. A certain
simple technic of depressing a single key at a
amount of leakage through the wiring and par
time is easily mastered. In case at any time acci
ticulariy through the keyboard contacts is prac
dentally. or intentionally more than one key is
tically unavoidable. particularly in humid
depressed at the same time, the highest key will
weather. This is substantially compensated for 55 be
the controlling one, while the others have
by voluntarily introducing a leakage path of
practically no effect on the resulting note. This
constant value which is much lower than the
will be readily understood from the circuit shown
accidental and variable leakage in the circuit.
in Fig. 1. Provided that switching key 3! is
Experience has demonstrated that this simple
in the high range, resistances l0 and
‘expedient practically completely eliminates all
II will be connected across condenser 20 through
difliculties heretofore experienced in the, con
a balancing resistance 40 and an individual tun
stancy of tuning under unfavorable atmospheric
ing potentiometer II. If now also switching key
30 will be simultaneously depressed, this will cause
additional connection of resistances 3! and it
From the foregoing description, the operation 85 but these, having a value of several hundred
thousand ohms will be practically short circuited
of the electrical musical instrument embodying
by the low resistance ‘path through a balancing
the principles of the present invention will be
resistor ll, two potentiometers II and another
- balancing resistor III. This path is hardly in ex
Ttmingoi’theinstrumentiscarried out atthe
factory by employing a conventional musical 70 cess of 50,000 ohms.
'I'hesameapplies when any number of keys is
instrument of very constant tuning, such as a
depressed at the same time, always the highest
reed organ, for standard. or by means of the
same method as is now generally employed by
note will sound and at no time will be non-har
monic notes foreign to the scale produced. This
trained piano or organ tuners. First of all, the
general or standard pitch of the instrument is 75 circumstance is of great importance as in normal
> . 2303,00‘
playing, particularlyi'in legato passages, the si-
extremely helpful for experi
the ?lter system necessary
multaneous depression of two keys at least tran
siently canbe hardly avoided. This problem was
quite serious inthe art and to avoid the produc
to obtain a I certain de?nite tone color.
sands of combinations can be tested within a few
tion of non-harmonic. notes upon transient de
pression of two keys at the same time some in
hours, and/Jae soon as a tone quality of attractive
timbre is found, the particular ?lter may be read
ventors were forcemtof include complex switching
ily built up in the,‘ form or a ?xed stop, if desired.
devices into the instrument which upon depres
sion of more than one key ‘at a time completely
01' course, the number of taps on each switch '
be increased‘; over six in order to accommo
de-energize the system and prevent production 10 =may
date ni, re electrical elements such as‘inductances,
of any sound at all. 1:‘ Of course, this procedure
capacitors and resistances of different size. Any
does not provide anyisolution of the problem be
tone fcolor once/obtained may be reconstructed
cause when a legatdg‘passage is played, there will
in a/ifew seconds, if record is made of the tap
be a short intervali‘between passing from one
nunjibers to. which the respective switches have
note to the next in ii‘which nothing will be heard 15 ‘tonlbe set, each setting being characterized by six
and thereby it is inade impossible to obtain a
good legato ei’fectywhich is one of the principal
attractions of a sustained-note melody instru
characterizes a ?lter in which three inductances
modulated or embellished by means of a tremolo
not restricte' to my electrical musical instrument '
?gures. Thus] to rexample, the ?gure 222,533
‘are connected in the horizontal or series portion
ment. The present invention provides a com-'
of the ?lter, and a condenser is connected after
plete solution for this problem.
20 each inductance to ‘ground. Obviously, the use- '
The sustained note of the instrument may be
fulness of my novel universal tone ?lter ‘device is
effect by placing e?’ect switch 55 into its upper
but can beil'i‘sea with good results in any electrical
position, or may be caused to imitate a plucked
musical 1 , trument in which the oscillators ini
string by utilizing a banJo eil'ect by placing said 25 tially produce oscillations vof relatively complex '
wave i'orn’i.
switch into its lowermost position. In the center
or neutral position of thee?ect switch the pro
Altholrgh the present invention has "been de-_'
duced note is unmodulated.‘ The various tone
colors may be readily and selectively obtained by
actuating one or more-of stop buttons l to 0
scribed in connection with certain preferred em
bodiments thereof, variations and modi?cations
may be’ resorted to by those skilled in the art‘
without departing from the principles oi’ the
' individually or in combinations, as it has been
> set forth more ‘fully in the foregoing.
present invention. I consider all oi'vthese varia
In some cases, it has been found desirable to
tions (and modi?cations to be within the 'true'
provide ?ltering means, capable of producing any
desired tone color by means of suitable adjust
ment thereof. A device of this type may be used
in addition to the ?xed ?lters described in the
spirit and scope of the present invention, as dis- '
closed in the foregoing description and de?ned
byf/the appended claims.
1. An electrical musical instrument employing
electro-acoustic transducer, said instrument
stops, such timbre may be readily obtained by 40 an
comprising in combination a space discharge de
foregoing so that when a tone color or timbre is
desired which is not included among the fixed
means of a few simple adjustments. A universal
vice, a tuned mesh for said- space discharge de-
tone ?lter which has been found to provide ex
cellent results is diagrammatically illustrated in
Fig. 3.
As it will be readily observed in Fig. 3, my
novel universal tone ?lter comprises six, or more,
tap switches “8 to I23. Each of these tap
switches has six contact points I to l. Threeof
the switches H0, H0 and I20 are connected in
series and form the horizontal portion of the re
sultant ?lter, and the rest of the switches l2l,
I22, and I23 are connected across the elements
of the horizontal portion and the common ground
lead I“. Each tap switch is capable of connect
ing various electrical elements, such as induct
ances, capacities and resistances of appropriate.
value into the ?lter circuit. For example, the
respective values of inductances may be 0.5 to 2
henries oi’ the capacitors 0.001 to 0.006 mi. and of
the resistances 10,000 to 50,000 ohms. In addi
tion, one of- the taps of each horizontal switch
may have a tap connected to a shorting lead I25,
while the ?rst tap of the vertical switches may
be open. As those skilled in the art will readily
understand, a device of this type is capable of
providing ?lter combinations‘of an almost in
?nite number, more than one hundred thousand
for the described number of taps, in which ?lters
vice, and including variable resistances connect
. ed in parallel, switching means for connecting se
lected resistances of said mesh into oscillation
producing relation with said space discharge ‘de
vice, a conductive path connecting said trans
ducer in the outputof said device, range-shifting
means for said device, and correction means in'- ‘
dividual for each range to eliminate the e?’ect of
variables incidental to the change of range.
2-. An electrical musical instrument employing
an electro-acoustlc transducer, said instrument
comprising in combination a space discharge de
vice,‘a series of tuning elements for said device.
‘manually operable elements for‘ connecting-se
lected portions or said series in oscillation-pro
ducing relation with saidv space discharge device
thereby to selectively produce frequencies ap
proximately corresponding to notes of the tem
pered scale, a conductive path connecting the
aforementioned transducer in the output of said
device, range-control means for rendering said
series operative in a plurality or ranges, and in
‘ dividual tuning means for each of said ranges to
accurately adjust the resulting frequencies.
3. A solo electrical musical instrument em
ploying an 'electro-acouiltic tranducer, said in
strument comprising in combination a glow-div‘
inductances, resistances and capacities may be
charge tube, a conductive path connecting said ~
connected in all conceivable ways. In general, 70 transducer in the output of said glow-discharge
each combination produces a di?erent tone color
tube, a tuned mesh for said tube and including
when connected into the output circuit of the
variable resistances connected'in parallel, switch
instrument of the invention. The universal tone
ing means for selectively connecting resistances
control device of the invention is not only useful
of said mesh to said tube to approximately tune
as an addition to any electrical musical instrw-v
the ‘same to frequencies corresponding to notes
. .
o: the tempered scale with in a range, means for
shifting said range, and a set of individual tun
ing elements for each range for accurately ad
for neutralizing the effect of the setting of the
set de-energized potentiometers upon the set of
energized potentiometers.
7. A solo electrical musical instrument includ-,
ing an electro-acoustic transducer, said instru
4. A solo electrical musical instrument employ
ment comprising in combinationa glow-dis
ing an electro-acoustic transducer comprising in
charge tube having capacitive means connected
combination a glow-discharge tube, a conductive
in series therewith, a conductive path connecting
path connecting said transducer in the output of
the transducer in the output of said glow-dis
said glow-discharge tube, a series of resistances
and a plurality of valuable condensers for said 10 charge tube, a series of tuned resistances, note
switching means for selectively connecting a se
tube, switching means for connecting selected
lected plurality of said series across said capaci
portions of said series in oscillation-producing
tive means and in oscillation-producing relation
relation with said tube thereby to approximately
with said tube thereby to cause said tube to pro
tune the same to frequencies corresponding to
notes of ‘the tempered scale within a range, 15 duce oscillations approximately corresponding to
notes of the tempered scale within a determined
switching means in selective coaction with said
iusting the frequencies produced.
condensers to shift the range of said notes by a
fixed amount, a set of individual tuning ele
range, range-switching means for changing the
effective capacitnace value 01' said capacitive
means and thereby to shift said range by at least
ments for each range for accurately adjusting
the frequencies, and means (or rendering said 20 one octave, a set of individual tuning potentiom
eters for each range to accurately adjust the fre
sets selectively operable concurrently with the
quencies produced, means selectively energizing
shifting of range.
said sets oi’ potentiometers in accordance with
5. A solo, electrical musical instrument em~
the range which isoperative, and balancing re
ploying an electro-acoustic transducer, saidin
strument comprising in combination a glow-dis 25 sistances interposed between said potentiometers
and said switching means for neutralizing the ct
charge tube, a conductive path connecting said
fect of the setting of the tie-energized potentiom
transducer in the output of said glow-discharge
eters upon the energized potentiometers, said
tube, a condenser in series with said tube and a
tuned resistances being considerably higher in
plurality of serially connected resistances,
switching means for selectively connecting a se 30, value than said balancing resistances and said
balancing resistances being considerably higher
lected portion of said plurality across said con
in value than said potentiometer.
denser and in oscillation-producing relation with
8. A solo electrical musical instrument em
said tube thereby to cause said tube to produce
ploying an electro-acoustic transducer, said in
oscillations of different frequencies within a de
termined range, switching means for changing as strument comprising in combination a glow-dis‘
the capacity of said condenser and thereby to
charge tube, a tuned mesh for said tube, said
change said range by at least one octave, a set
mesh including a plurality of resistances in par’
allel, note-switching means for said mesh for
of individual tuning potentiometers for each
connecting any selected resistance in oscillation
range to accurately adjust the rrequencies pro
duced, and means for selectivehv energizing said 40 producing relation with said tube thereby to
cause production‘ of oscillations of step-by~step
sets of potentiometers in accordance with the
range'which is operative.
8. A solo electrical musical instrument‘ em- '
ploying an electro-acoustic transducer, said in
strument comprising in combination a glow-dis
charge tube, a conductive path connecting said
transducer in the output of said glow-discharge
tube having capacitive means connected in se
ries therewith, a series of resistances, switching
means for selectively connecting a selected plu
rality or said series across said capacitive means
and in oscillation-producing relation with said
tube thereby to cause said tube to produce oscil
lations approximately corresponding to notes of
the tempered scale within a determined range,
switching means for changing the effective ca
pacitance value, oi‘ said capacitive means and
thereby to shift said range by at least one octave,
a set of individual tuning potentiometers for
each range to accurately ‘adjust the frequencies
produced, means for selectively energizing said
sets, of potentiometer: in- accordance with the
range which is operative, and balancing means
varying frequencies within a range, means for
shitting said range in octave steps, a set of poten
tiometers for each range to accurately adjust
said frequencies, means for rendering said sets
selectively operative in accordance with the
range, means for neutralizing the effect of the
inoperative set of potentiometers upon the ener
gized set of potentiometers, and means effective
'- for all ranges for continuously adjusting the gen
eral pitch of the instrument.
9. In an electrical musical instrument includ
ing, an electro-acoustic transducer and a glow
dls'charge tube oscillator tunable in steps by
.means or a tuned mesh including a set of re
sistances connected in parallel and keying means
for connecting any selected resistance in circuit
with said tube, a resistance of the order of about
500 megohms to about 2,000 megohms connected
across the electrodes of said tube thereby to neu
tra'lize the eifect of leakage on the constancy of
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