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Патент USA US3093710

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June 11, 1963
T. .1. GEORGE
3,093,700
ELECTRONIC TREMULANT SYSTEM
Filed Sept. 21, 1959
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INVENTOR.
June 11, 1963
3,093,700
T. J. GEORGE
ELECTRONIC TREMULANT SYSTEM
Filed Sept. 21, 1959
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‘3,093,700
United States Patent Oii ice
Patented June 11, 1963
2
2.
heaviest permissible vibrato may still leave the listener
3,093,700
Thomas J. George, Los Angeles, Calif.
(11671 Victory Blvd., North Hollywood, Calif.)
with the feeling that an even heavier beat could be desir
ELECTRONIC TREMULANT SYSTEM
able. Thus in accordance with this invention, if when
the maximum permissible vibrato is in use, a synchronized
Filed Sept. 21, 1959, Ser. No. 841,244
4 Claims. (Cl. 84—1.22)
This invention relates in general to electronic organs,
and in particular to a simpli?ed tremulant system for
such instruments.
10
Nearly all electronic organs now commercially avail
tremulant beat of a type to be disclosed herein, is added
to the vibrato beat, a heavy theatrical effect will result.
Furthermore this heavy tremulant heat will not contrib
ute to the “out of tuneness” mentioned above, because
the tremulant is not a change in pitch, but a change in
amplitude.
1
However, to add to the vibrato a tremulant of the type
wherein the amplitude of the signal merely rises and falls
cyclically, does not result in much improvement. Ac
periodic change in the pitch of the tones of the instru
cordingly, a tremulant system is herein disclosed, wherein
ment, while tremulant is de?ned as a periodic change in 15 the organ signal is amplitude modulated completely, and
able are equipped with some form of musical vibrato in
stead of tremultant. Vibrato is commonly de?ned as a
the amplitude of the tones, or in brief, vibrato is fre
quency modulation, and tremulant is amplitude modula
tion of the musical tones. The frequency of these pe
riodic changes, or beats, iies usually between approxi
mately ?ve and one half to seven and one half cycles per
second.
at the same time the phase of the signal is reversed twice
in every tremulant cycle.
This system should not be
confused with various phase shift methods of the prior
art. The present invention does not shift the phase and
there is no change in velocity of vector rotation to any
signi?cant degree.
Rather there'is a complete ampli
tude modulation accompanied by a reversal of phase,
In the pipe organ, the tremulant or vibrato is usually
and this will be more ‘fully explained.
effected by a periodic change in the pressure of the wind
which is blowing the pipes. This causes both the pitch
Hereinafter the normal tremulant rate will be referred
and the loudness of the pipe tone to change periodically. 25 to as six cycles or beats per second, but it will be under
stood that any generally accepted tremulant rate may be
It is apparent therefore, that to more nearly vapproach
used, and may lie anywhere between approximately ?ve
the musical effect produced by the pipe organ, the tones
and one half to seven and one half cycles per second.
of the electronic organ should cyclically change in both
So far as I am aware no intrument has heretofore been
pitch and loudness, and this result will in fact be achieved
if both vibrato and tremulant are present in the tones of 30 devised in which vibrato or frequency modulation, and
tremulant or amplitude modulation, are both provided,
the electronic organ.
and which may be used separately or together in selected
\In the entertainment type, or so called theatre pipe
amounts.
organ, it is customary to provide, for certain effects, a
Thus in accordance with the invention, a principal ob
very heavy tremulant, and in fact this has come to char
acterize this type organ. This type of theatrical tremu 35 ject is to provide means whereby a tremulant may be
used separately or in conjunction with the normal vibrato
lant is very popular, especially when used with certain
of an electronic organ, and to ‘a degree selected by the
types of tone, such as ?ute. Some types of organ pipes,
player.
such as string or reed, with a given change in wind pres
Another object is to provide means for a so called
sure, will produce more change in pitch than other types.
stereophonic tremulant which obviates the monotony of a
On the other hand, other pipes such as ?utes produce
simple amplitude tremulant, by causing a continuous three
more change in amplitude and less pitch change, with a
dimensional change in acoustic room pattern. This‘stereo
given change in wind pressure.
'
phonic tremulant has as one of its principal features the
In electronic organs, usually the same vibrato is applied
production of a secondary tremulant beat in addition to
to all voices, and in most of these organs little or no
tremulant is present other than that which occurs as a 45 the normal or primary tremulant beat. The function and
operation of this secondary beat is described in detail
result of acoustic room pattern.
in my United States Patent 2,780,302, and in that patent
Apparently because of the frequency response charac
the effect is produced by purely mechanical-acoustical
teristics of the human ear, as well as other psychological
factors, more actual change in frequency is required with 50 means. In the present disclosure the effect is produced
by electro-acoustical means. In brief, it has been observed
?ute tone, than with string tone for example, to produce
that part of the heavy tremulant beat of the theatre or
an equivalent subjective vibrato effect. This is probably
gan is occurring at double frequency or about twelve
due to the fact that ?ute tone is relatively pure, with but
beats per second. This beat rate may be thought of as
few harmonics. String tone is very bright, with complex
harmonic structure, and it is probable that the ear more 55 being superimposed upon the normal six cycle beat, or
readily perceives the pitch movement of the higher order
harmonics of the bright string tone. However it is ob
servable, that when using ?ute tone, a heavy tremulant
is subjectively practically equivalent to a heavy vibrato,
and this is consistent with the heavy tremulant used with
?ute voices in the theatre pipe organ.
The limiting factor in the maximum amount of vibrato
which is useful is an apparent “out of tuneness” which
occurs when the periodic pitch change becomes too great.
. it may be considered to be a light secondary beat spaced
alternately in time with the normal primary beat.
In the present invent-ion, the tremulant effect is the re
sult of acomposite acoustic signal. In part of this sig
nal which is radiated ‘from one loudspeaker, the signal
voltage is caused to reverse in phase approximately twelve
times per second, or twice in every normal tremulant cy
cle. The other part of the signal which is radiated from
a second speaker, is of constant unchanging phase and
To some extent this is a matter of personal taste, and 65 amplitude. The two parts are thus combined acoustically.
will vary for different individuals. However, it is cer
tainly true that a too heavy vibrato is more objectionable
with a bright tone than with a pure tone. This leaves
During one half the tremulant cycle, the two parts are
in phase and are additive. During the other half cycle
the signals are of opposite phase, and tend to cancel
one another. When the two parts are thus combined
many listeners with the feeling that the heaviest permis
sible vibrato for bright voices in the electronic organ, is 70 acoustically, the addition and cancellation of the signals
occurs in the air, with a pleasing three dimensional or
still not heavy enough for pure voices such as ?ute and
stereo effect.
7
even diapason. In other words, for theatrical effects, the
3,093,700
3
4-
7
Another object therefore is to provide simpli?ed means
generator are connected through the voltage divider,
for reversing the phase of part‘ of' the signal twice in
comprising resistors ‘12 and 13, to input grid 11 of tube
1. During the positive half cycle of vibrato voltage,
every tremulant cycle.
Another object is to electrically combine the phase re
versing signal with the steady unmodi?ed signal to' pro
duce a pleasing tremulant.
the tube will amplify the organ signal, and an ampli?ed
output signal will appear at anode 5., and hence at out
put terminal X. This signal will have the appearance
of a completely modulated envelope similar to that shown
Other objects will appear from the following descrip
tion, reference being had to the accompanying drawings
in curve C.
This curve indicates that there is no out
in which:
put signal during the negative half cycle of vibrato sig
FIGURE 1 is a schematic of the circuit used for re 10 nal voltage. The shaded portion of the envelope above
versing‘the phase of the organ signal in one form of the
the zero axis represents the area of negative swing of
invention.
the modulated organ signal voltage, and the unshaded
FIGURE 2 is illustrative of the various signal envelopes
portion below the axis is the area of positive swing of
employed in the practice of the invention.
this voltage. The frequency of the organ signal is not
FIGURE 3 is a block diagram of a preferred form 15 important. Curve D shows the envelope of the un
of the invention.
modulated organ signal appearing at the input terminal
FIGURE 4 is a block diagram of a modi?ed form of
Z. Note that the unshaded positive area is above the
FIGURE 3.
axis and the shaded negative area is below the axis,
Referring to FIGURE 1, a phase reversing circuit is
which is the reverse of curve C. A part of the direct
shown which operates as follows. A multi grid tube
organ input signal is carried from input’ terminal Z to
such as a type '6BY6 is shown at 1. This tube is con
the anode ‘5 through variable resistor 21 and blocking
nected as a variable gain audio ampli?er. Its cathode‘
capacitor 20, and the amount of direct unmodulated or
2 is grounded through resistor 3, which is bypassed by
means of capacitor ‘4. Theanode 5 is connected by
gan signal which appears at the anode is controlled by
the selected value of resistor 21. It will thus be under
means of plate resistor 6 to B plus supply 7. The screen 25 stood that the signal appearing at the ‘anode 5, and at
grid 8 is connected to the B plus supply 7 through re
sistor 9, and is bypassed to ground'lby means of ca
pacitor \10. The signal grid 11 is connected through re
the o-utput‘terminal X at any moment is a composite
signal, which is the instantaneous algebraic sum of the
direct organ signal, and the amplitude modulated organ
sistor 12 to input terminal Z, and is returned to ground
through resistor 13. The injector grid '14 is connected
signal. Because of the phase inverting action of tube 1,
the modulated organ signal is opposite in phase to the
through capacitor 15 and resistor 16 to vibrato signal
direct organ signal, which undergoes no change in phase.
This is illustrated in the envelope curves C and D in
FIGURE 2. The composite ‘algebraic sum “of curves C
input terminal Y, and is returned to ground through
resistor 17 and capacitor 18‘ in parallel. The anode 5
connects to output terminal X through capacitor 19 and
and D is shown in curve E. Assume that the maximum
adjustable voltage output control 22. Anode 5 is also 35 amplitude of the modulated output signal, curve C, is
connected to input terminal Z through capacitor 20 and
approximately twice the amplitude of theunmodulated
variable resistor 21 connected in series.
input‘signal, curve D. Then, since the signals are op
As the circuit is normally used, the output signal from
posite in phase, cancellation will take place during the
the organ tone generator is connected to input terminal 40 ?rst half of the tremulant cycle, the interval from r to
Z. In most electronic ‘organs, 1a low frequency oscillator
s. The resultant signal will be of half the amplitude of
is provided which generates a vibrato signal of approxi
the modulated signal C and of the same phase.
mately six cycles per second. The output ‘signal from
During the second half of the tremulant cycle, the in
this oscillator is used within the organ for effecting a
terval from s to t, the tube is cut off, and no modulated
vibrato or frequency modulation of the signals from the 45 output signal appears at the anode 5, but only the di
tone generators in the organ. A connection is made, as
rect organ signal. The direct signal appearing at the
anode and output terminal X during the second half
shown, between the six cycle oscillator'39 and'the vibrato
signal input terminal Y. This connection provides“ a six
cycle control voltage which is used to vary the ampli?
of the tremulant cycle will therefore be of approximately
equal amplitude, but of opposite phase to that which
cation of tube 1. In order to obtain a tremulant which
50 appears during the ?rst half cycle. The result is the
is synchronized with'the organ vibrato, it is necessary
to obtain the six cycle control signal from the organ
vibrato circuit. However, it should be understood that
if it is not desired to synchronize‘ the tremulant with
double lobed envelope of ‘curve E. This curve illustrates
that the composite output signal from the tremulant cir
cuit rises to a peak every 3/12 second, or twice in every
tremulant cycle, and that the ?rst and second peaks are
the vibrato, or if the tremulant'circuit is to be used
with an instrument which does not have a vibrato, such
as ‘a guitar, piano, or reed organ, then the six cycle con
trol signal may be taken from‘ any convenient so'urce.
Resistors 16 and 17 are selected so that the vibrato
control signal at the injector grid 14 is approximately
two volts. The voltage at grid 14 will thusrrise’ and
fall six times per second. When it is maximumrin a
positive direction, the gain of tube '1' will be 'a' maximum.
When the voltage at ‘grid 14 is maximum in a negative
direction the gain of tube 1 will ‘be zero and the tube
will be cut off.
In FIGURE 2, at curve A is shown one cycle of ‘the
of opposite phase. The relative amplitudes of the ?rst
and second peaks are controlled by means of variable re
sistor 21, and the peaks are adjusted to be of approxi
mately equal amplitude when it is desired to obtain the
Y secondary tremulant beat described in the previously men?
so
tioned patent.
The voltage divider comprising resistors 12 and 13 is
an important aspect of the invention and its function is
explained as follows. Its primary purpose is to isolate
~ the anode circuit from the grid ‘11.
If this were not
done, then the feed~forward path through resistor 21
and capacitor 20 would form a very effective negative
feedback means, and the tube could not function in the
vibrato control voltage, and the time interval is approxi
manner described. This divider therefore is a very im
mately one sixth second.‘ Immediately below, curve B
shows how the relative gain of the tube varies with 70 portant part of the tremulant circuit. The second pur
pose of the divider is to reduce the input voltage to grid
vibrato signal voltage, reaching a maximum during the
11 in order to avoid distortion. Capacitor 19 is selected
positive half cycle, and being reduced to zero during the
to be of a value small enough to attenuate any six cycle
negative half cycle. Since the tube is cut off during the
component in the output voltage, yet not small enough
negative half cycle, the output signal appearing ‘at anode
5 is discontinuous. The signals from the organ tone 75 to‘ seriously impair the bass notes of the organ tones.
3,093,700
.
5
t
-
The following table gives values ‘for the components
ing ampli?er and speaker 34 and 35. If this is done
which are used in the circuit of FIGURE 1:
3
10K.
4
5 mi.
6
560K.
7
B plus 250 v.
9
1 meg.
10
‘.05 mf.
then lead 38 should be disconnected from tremulant in
put terminal Z, and connected instead to output terminal
X, as shown in FIGURE 4. With this arrangement it
may be desirable to readjust slightly control 21. ‘This
will make the secondary tremulant beat less prominent,
by making one or the other lobe larger in curve B. It
'will be seen that by adjusting this resistor to a small
value, the tremulant Ibeat may be eliminated, because
the modulating circuit is bypassed. Thus with this ar
rangement, variable resistor 21 controls the degree of
tremulant, and ampli?er and speaker 26 and 27 repro
12
l meg.
13
15
220K.
.05 mf.
16
17
1'3
1 meg.
1 meg.
.05 mi.
19
20
21
__; .006 mi.
.05 mi.
500K.
22
___ 100K.
duce the organ tones, either with or without tremulant.
‘ In using this tremulant system with an electronic or
gan, it will be apparent that many possible combinations
of tremulant and vibrato may be used. The organs own
vibrato may be used without tremulant. The tremulant
may be used in varying degrees with the organ vibrato
. turned off.
The tremulant may be used in combination
FIGURE 3 is a block ‘diagram showing the manner in 20 with the organ vibrato, and when they are both set to
maximum a very heavy theatrical beat will be obtain
which the tremulant circuit of FIGURE 1 will normally
be used with an electronic organ. An electronic organ
able.
What are considered to be the novel features of this
is indicated at 23, having a keyboard 24, a tone gen
disclosure are:
erator 25, an ampli?er 26, and an acoustical transducer
(1) Means ‘for providing in an electronic organ, both
such as speaker 27. The tone generator has a signal 25
tremulant and vibrato, which may be used separately or
output terminal 31 which is connected to the input ter
in combination.
minal Z of the tremulant circuit 33. The tone gen
(2) A simple one tube circuit capable of reversing
erator also has a vibrato signal voltage output terminal
the phase of the organ signal approximately twelve times
30 which is connected to the vibrato signal input ter
minal Y of the tremulant circuit. The organ ampli?er 30 per second.
26 has an input terminal 28 which is connected to the
tremulant circuit input terminal Z by means of lead 38.
(3) Means for providing a tremulant having a sec
ondary beat.
(4) Means for combining a modulated signal of one
The output of the ampli?er 26 is connected to organ
phase with a steady signal of opposite phase to obtain a
speaker 27. The output terminal X of the tremulant
circuit is connected to the input terminal 36 of a sec 35 tremulant.
(5) Means for acoustically combining an amplitude
ond ampli?er 34. The output of ampli?er 34 is con
modulated signal of one phase with a steady signal of
nected to a speaker 35.
opposite phase for obtaining a stereo tremulant e?ect.
In operation of the circuit of FIGURE 3, the signals
It will be understood that while I have shown and de
from the organ tone ‘generator are ampli?ed and repro 40
scribed preferred embodiments of my invention, it will
duced by the organ ampli?er and speaker 26 and 27.
be apparent to those skilled in the art that numerous
The tone generator output signals are simultaneously
variations and modi?cations may be made, such as the use
modulated by means of the tremulant circuit 33 in the
of transistors, varistors, or other modulating means, with
manner previously ‘described, and the modulated output
signals are ampli?ed and reproduced by means of the 45 out departing 'from the basic principles of the invention. I
ampli?er and speaker 34 and 35. Speaker 35 may be
mounted in the organ with speaker 27, or it may be
mounted in a separate tone cabinet.
An unmodu-lated organ signal represented by curve D
of FIGURE 2 will be reproduced by organ speaker 27,
and the double lobed signal of curve E will be repro
duced by speaker 35. The relative loudness of the two
signals may be adjusted by means of output control 22
of FIGURE 1. When they are of about equal loud
therefore desire, by the ‘following claims, to include With
in the scope of my invention all such equivalent or similar
constructions whereby substantially the same results may
be obtained by substantially the same or equivalent means.
Having thus described my invention, I claim as follows:
1. A tremulant circuit for musical instruments com
prising an audio signal source, a vibrato oscillator signal
source, a single stage variable gain ampli?er having an
output and ?rst and second inputs for combining said
ness, a heavy tremulant beat will be heard which can 55 audio signal and said vibrato oscillator signal to pro
duce a discontinuous signal of opposite phase from said
be represented approximately by curve F of FIGURE
audio signal, means connecting said audio signal source
2. This curve is representative of the composite modu
to said ?rst input, means connecting said vibrato oscil
lated acoustic signal envelope occuring at some point
lator source to said second input and a vfeed-forward path
in the listening area, and it may be observed by the use
of a microphone and an oscilloscope. However, it is 60 connecting said source of audio signals to the output of
only representative, since acoustic room pattern varia
tions will change the curve shape in different parts of
the listening area. Note also that the phase position dur
ing the ?rst half of the tremulant cycle is reversed dur
said variable gain ampli?er without changing the phase
of said audio signal, whereby said discontinuous signal
and said audio signal are combined to produce a tremulant
signal of desired characteristic.
2. A tremulant circuit for musical instruments com~
ing the second half of the cycle. These two e?iects com 65
prising an audio signal source, a vibrato oscillator signal
bine to produce a stereo-tremulant e?ect because the
source, a single stage variable ‘gain ampli?er having an
room pattern is never the same at any given instant for
output and ?rst and second inputs for combining said
the listeners two ears, and the result is a very pleasing
audio signal and said vibrato oscillator signal to pro
three dimensional movement of the organ tones.
The degree of tremulant employed may be selected 70 duce a discontinuous signal of opposite phase from said
audio signal, means connecting said audio signal source
by the adjustment of tremulant output control 22, and
to said ?rst input, means connecting said vibrato oscil
the degree of the secondary beat e?ect may be selected
lator
source to said second input, a feed-forward path
by means of control 2.1.
connecting said audio signal source to the output of said
If it is desired for the sake of economy, not to in
corporate the stereo feature, this may be done by eliminat 75 variable gain ampli?er without changing the phase of said
3,093,700
7
8
audio signal, and means effectively isolating said feed
audio signal sourceto the output of said?rst ampli?er
means Without changing the phase of said audio signal,
forward path from said ampli?er topreventvfeedback,
whereby said discontinuous signal and said audio signal
are combined to produce a tremulant signal of desired
characteristic.
‘
I
second and third ampli?er means‘, means‘ connecting said
audio signalts‘ource to said second ampli?er means, means‘
connecting saidq?rst ampli?er output to said third ampli
3. In an electronic organ an audio signal source, a
?er means,,?rst. acoustical transducer, means connected to
vibrato oscillator signal source, ?rst ampli?er means hav
ing an output and a plurality of inputs ‘for combining
said audio signal and said vibrato‘v oscillator signal to
produce a discontinuous signal of opposite phase from 10
said audio signal, a ‘feed-forward path connecting said '
audio signal source to the output of said ?rst ampli?er
means Without changing the phase of said audio signal,
second ampli?er means‘, means connecting ‘said ?rst
said second ampli?er means, and, second acousticaltrans
ducer means connected to said third amp1i?er__means,
whereby the acoustical, signals generated by saidtrans
‘ducers will combine to produce a desired stereo trem
ulant e?ect.
References Cited in the ?le of this patent
UNITED
PATENTS
ampli?er output to said second ampli?er means, and 15
2,093,223
Yasmashita _______ __,-_,_ Sept._r1_4, 1937
acoustical transducer means connected to said second
ampli?er means to produce a musical sound having a
2,148,478,
Kock _____ ____ _,_,_ ______Feb. 28, 1939
2,245,354
__
,_ _--.- June 10,1941.
desired tremulant effect.
4. In an electronic organ an audio signal source, a
vibrato oscillator signal source, ?rst ampli?er means hav 20
ing an output and a plurality of inputs for combining
said audio signal and said vibrato oscillator signal to
produce a discontinuous signal of opposite phase from
said audio signal, a feed-forward path connecting said
2,342,286
v
.
,—.-~-*—r'r—.——
4 ------- -.-- 'Febl
1.944
2,758,204
Norby ________________ __ Aug, 7, 1956
2,817,708
‘Fender __j__‘_____‘____'___ Dec. 24, 1957
2,835,814
Dorf __‘__'__‘__;____‘__"____ ‘May 20, 1958
2,845,491
Bertram ___‘___'____“____ July 29, 1958
2,883,625
Sparks __‘_____________ __' Apr. 21, 1959
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