US3778525A - Electronic musical instrument with phase shift tremulant system - Google Patents

Electronic musical instrument with phase shift tremulant system Download PDF

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Publication number
US3778525A
US3778525A US00244573A US3778525DA US3778525A US 3778525 A US3778525 A US 3778525A US 00244573 A US00244573 A US 00244573A US 3778525D A US3778525D A US 3778525DA US 3778525 A US3778525 A US 3778525A
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phase shift
phase
channel
signal
channels
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W Chase
B Plunkett
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Thomas International Corp
Kimball International Inc
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Thomas International Corp
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H1/00—Details of electrophonic musical instruments
    • G10H1/02—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos
    • G10H1/04—Means for controlling the tone frequencies, e.g. attack or decay; Means for producing special musical effects, e.g. vibratos or glissandos by additional modulation
    • G10H1/043—Continuous modulation
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
    • G10H2210/155—Musical effects
    • G10H2210/195—Modulation effects, i.e. smooth non-discontinuous variations over a time interval, e.g. within a note, melody or musical transition, of any sound parameter, e.g. amplitude, pitch, spectral response or playback speed
    • G10H2210/201—Vibrato, i.e. rapid, repetitive and smooth variation of amplitude, pitch or timbre within a note or chord
    • G10H2210/205—Amplitude vibrato, i.e. repetitive smooth loudness variation without pitch change or rapid repetition of the same note, bisbigliando, amplitude tremolo or tremulants
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
    • G10H2210/155—Musical effects
    • G10H2210/195—Modulation effects, i.e. smooth non-discontinuous variations over a time interval, e.g. within a note, melody or musical transition, of any sound parameter, e.g. amplitude, pitch, spectral response or playback speed
    • G10H2210/201—Vibrato, i.e. rapid, repetitive and smooth variation of amplitude, pitch or timbre within a note or chord
    • G10H2210/211—Pitch vibrato, i.e. repetitive and smooth variation in pitch, e.g. as obtainable with a whammy bar or tremolo arm on a guitar
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10H—ELECTROPHONIC MUSICAL INSTRUMENTS; INSTRUMENTS IN WHICH THE TONES ARE GENERATED BY ELECTROMECHANICAL MEANS OR ELECTRONIC GENERATORS, OR IN WHICH THE TONES ARE SYNTHESISED FROM A DATA STORE
    • G10H2210/00—Aspects or methods of musical processing having intrinsic musical character, i.e. involving musical theory or musical parameters or relying on musical knowledge, as applied in electrophonic musical tools or instruments
    • G10H2210/155—Musical effects
    • G10H2210/195—Modulation effects, i.e. smooth non-discontinuous variations over a time interval, e.g. within a note, melody or musical transition, of any sound parameter, e.g. amplitude, pitch, spectral response or playback speed
    • G10H2210/201—Vibrato, i.e. rapid, repetitive and smooth variation of amplitude, pitch or timbre within a note or chord
    • G10H2210/215—Rotating vibrato, i.e. simulating rotating speakers, e.g. Leslie effect
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S84/00—Music
    • Y10S84/01—Plural speakers

Definitions

  • a tremulant circuit includes cascaded phase shifting 178, 66; 332/3, l6, 17, 21, 22, 23 R; networks in right and left amplifying channels of an 250/199, 217 R electronic organ.
  • An oscillator and associated circuitry produce offset signals of different wave shape [56] References Cited which energize lamps associated with light responsive UNITED STATES PATENTS impedances in the phase shifting networks in the right 2 892 372 6,1959 Bauer 84/115 and left channels.
  • a switching circuit interconnects 0/1961 Jones 34/101 the phase shifting networks in different configurations 3,004,460 10/1961 Wa ne," 84/10] to adapt the tremulant effect to a selected organ voice 3,007,361 11/1961 Wayne... 84/101 in order to produce the most pleasing and realistic 3,378,623 4/1968 Park 84/l.l8 acoustical output. 3,388,257 6/1968 TenByck...
  • the usual prior method has been to vary the frequencies of the master oscillators by a predetermined amount at a rate of about 6.7 Hertz. This causes the pitch of the note produced to vary above and below the nominal frequency at the desired rate of 6.7 Hertz.
  • the usual prior method has been to vary the gain of the organ amplifier circuitry at the desired rate of approximately 6.7 Hertz. This, of course, results in a variation in the amplitude of the tone produced, which cyclic variation occurs at the 6.7 Hertz rate.
  • phase shift system of the present invention has been developed. Briefly, a signal having a waveshape corresponding to a given musical tone is fed into a phase spliter. In the phase spliter, the signal is broken into two output signals; one of which is in-phase with and the second of which is 180 out of phase with the incoming signal. One output signal is then fed to a first phase shifter where it is cyclically retarded and advanced in phase at a rate of approximately 6.7 Hertz. The second signal from the phase spliter is fed to a second phase shifter, wherein it is likewise cyclically retarded and advanced in phase at the 6.7 Hertz rate. The outputs of the two phase shifters are then fed through separate amplifier channels to separate speakers.
  • the acoustical effect is that of a frequency deviation.
  • This frequency deviation arises because of the increasing and decreasing number of waveforms in transit between the speaker and the listener.
  • the magnitude of frequency deviation is proportional to the rate of change of phase and the amount of phase shift.
  • phase shift methods of producing the tremulant effect are relatively satisfactory, a number of problems have arisen, especially when the most pleasing and accurate reproductions are desired.
  • the different voices produced by the electronic organ differ in harmonic content.
  • the resulting acoustical effect may not be the most pleasing for such a voice due to the difference in phase shift between the harmonic and primary signals forming the voice.
  • the use of two reproduction channels, which is generally desirable for most tremulant effects, tends to produce an unpleasant sound for a violin voice.
  • a two channel phase shift method of producing tremulant is utilized.
  • a plurality of phase shift networks are cascaded.
  • Each network includes a light responsive resistor and an associated lamp coupled to a tremulant oscillator via appropriate circuitry.
  • phase shifting networks in different configurations. For example, the phase shift applied to a tibia voice approaches 720 in both the right and left channels, whereas a violin voice is shifted slightly less than 360 in only one channel. Each different voice is phase shifted to produce the most pleasing acoustical output effect.
  • the lamps in the two channels are driven by separate oscillator waveforms which differ in shape and are phase offset.
  • the phase shift produced in the right channel is not a duplication of, nor simply related, to the phase shift produced in the left channel.
  • voices processed by the two channels are acoustically combined, the resulting effect is most pleasing and has been empirically found to be superior to prior tremulant effects.
  • Various other modifications have been made to enhance the operation and resulting effect of the tremulant circuits, as will be explained.
  • One object of this invention is the provision of an improved tremulant circuit which selectively combines phase shifting networks in different configurations in order to tailor the tremulant effect to the instrument voice then being processed.
  • Another object of this invention is the provision of an improved two channel tremulant circuit, in which an oscillator and associated circuitry produce different waveforms for controlling the variable impedance elements in the two channels.
  • a further object of this invention is the provision of an improved tremulant circuit which produces a more pleasing tonal quality for a variety of organ voices than has heretofore been possible.
  • FIG. 1 is a block diagram of an electronic organ incorporating the applicants tremulant system
  • FIG. 2 is a partly block and partly schematic diagram of the tremulant system shown in block form in FIG. 1, and illustrating the phase spliter in detail;
  • FIG. 3 is a schematic diagram of the portion of the tremulant system which is shown in block form in FIG.
  • FIG. 4 is a simplified schematic diagram of a single stage of the phase shifter used in FIG. 3;
  • FIGS. 5A, 5B, 5C, SD, SE and SF depict waveforms illustrating the signals produced by the electronic organ shown in the remaining figures.
  • Each tone generator 20 also includes divider circuits which divide the master oscillator frequency by multiples of 2, and typically provide outputs corresponding to divisions by 2, 4, 8, and 16. Thus, each tone generator 20 produces frequencies corresponding to the indicated note in all five octaves on the organ keyboard.
  • Each of the five frequency outputs from all 12 tone generators 20 is fed to a distribution circuit 22.
  • the distribution circuit thus receives as inputs 60 signals, each signal having a frequency corresponding to the basic frequency of one note which can be played on the organ.
  • Distribution circuit 22 cooperates with keying circuitry actuated by a solo keyboard 24, an accompaniment keyboard 26, and a pedal keyboard 28, each of which pass signals having basic frequencies corresponding to the notes played by the organist. For example, if the key corresponding to the note E in the top octave of the solo keyboard is depressed, the circuit associated with keyboard 24 cooperates with distribution circuit 22 to pass a waveform having the appropriate basic frequency and harmonic content.
  • accompaniment keyboard 26 and pedal keyboard 28 is similar, as is well known.
  • the signal passed by solo keyboard 24 is a sawtooth wave, as shown at 30.
  • the sawtooth wave is simulated by adding together appropriate square wave signals produced by the tone generators 20 to form a stair-step waveform. It is desirable to pass a sawtooth wave at this point since such a waveform contains not only the basic frequency desired, but also all harmonics of that frequency. Thus, it is a waveform well suited for the further wave shaping which must be performed to simulate various voices to be produced by the organ.
  • a solo voicing circuit 34 is used to process the sawtooth wave passed by solo keyboard 24 such that a tone having a desired timbre may be produced.
  • voicing circuit 34 is a passive network having appropriate filter circuitry to selectively attenuate the basic and harmonic frequencies included in the sawtooth wave so as to produce various preselected timbres. For example, if the violin tab for the solo manual is depressed, appropriate filter circuitry will act on the basic and harmonic frequency content of the sawtooth wave such that amplification and reproduction of the resultant waveform will generate a sound having the timbre of a violin.
  • voicing circuit 34 is capable of acting on the incoming waveform such that tibia, violin, or complex voicing can be produced.
  • An accompaniment voicing circuit 36 and a pedal voicing circuit 38 perform corresponding functions for signals transmitted by the accompaniment keyboard 26 and the pedal keyboard 28, respectively.
  • the three signals emanating therefrom are individually fed to a corresponding solo tibia preamplifier 40, a violin preamplifier 42, and a solo complex preamplifier 44.
  • the signal which has been shaped by the accompaniment voicing circuit 36 is fed to accompaniment preamplifier 46.
  • These preamplifiers act to amplify the signals prior to further signal processing.
  • the appropriately shaped and amplified signals from circuits40, 42, 44 and 46 are passed to a manual balance control 50.
  • a resistive network including various potentiometers is used to balance the signal strength of the incoming signals, such that the outgoing signals are of the proper amplitude in relationship to each other.
  • the four signals corresponding to the tibia, violin, complex and accompaniment voicings are now passed over individual lines 52, 53, S4, and 55, respectively, to a tremulant switching circuit 60, forming part of the present invention.
  • Switching circuit is controlled by conventional rocker switches located on the cheek block of the organ.
  • the organist can determine whether the notes produced by the solo and- /or accompaniment manual will be passed through the phase shift tremulant circuitry of the present invention. If switching circuit 60 is preset to give a tremulant effeet to the solo voicing signal, for example, such signal will be fed into the the phase shift tremulant circuitry of the subject invention prior to further amplification by the organ amplifier circuitry. If the organist desires not to subject a given voicing to the tremulant effect, appropriate setting of the switches associated with circuit 60 will pass the signal directly to the nontremulant preamplifier 62 prior to further processing by the organ amplifier circuitry.
  • circuit 60 is set to produce a violin timbre in a non-tremulant mode.
  • the signal is transmitted out along a line 65 and is delivered only to a left channel preamplifier 66.
  • the signal is produced only by the left speaker of the organ. This result has been empirically determined to be musically desirable when a violin voicing is preselected.
  • voicing circuit 60 has been preset to give either a tibia or a complex voicing in response to playing of the solo manual, and that such voicing is to be produced without a tremulant effect.
  • the switching circuit 60 is preset to pass the signal waveform corresponding to the tibia or complex voicing along a line 68 to the nontremulant preamplibe passed via a line 70 to both the left channel preamplifier 66 and a right channel preamplifier 72.
  • the desired voicing will appear in both the left and right speakers, without the tremulant effect.
  • proper presetting of switching circuit 60 will also pass the accompaniment complex signal along line 68 to the nontremulant preamplifier 62.
  • the tibia waveform is transmitted on a line 75 directly to a right channel phase shifter 78 and a left channel phase shifter 80.
  • the right and left phase shifters 78 and 80 effectuate a cyclic advancement and retardation of the phase of the signal passing therethrough at a rate of about 6.7 Hertz.
  • the signal passing through the right phase shifter 78 is continuously advanced and retarded in phase as it is transmitted along an output line 82 to the right channel preamplifier 72.
  • the signal on line 75 which is supplied to the left phase shifter 80, is subjected to a similar continuous cyclical retardation and advancement in phase.
  • the resulting output signal on a line 84 is then separately coupled to the left preamplifier 66.
  • the output from the right preamplifier 72 and the left preamplifier 66 is independently amplified and coupled to separate right and left speakers.
  • the resulting acoustical effect is a cyclical variation in both frequency and amplitude, which, of course, constitutes the tremulant effect.
  • the cyclical variation in phase in the pair of phase shifters 78 and 80 is produced by a master tremulant oscillator 90 generating a left control signal which is coupled to a left channel lamp driver 92, associated with left channel phase shifter 80.
  • a second signal is transmitted through a double shape'r 94 to produce a different right control signal coupled to a right lamp driver 96 associated with right phase shifter 78.
  • the lamp'drivers energize lamps which control the impedance of light sensitive variable impedance elements in each of the phase shifters, which variable impedance elements are connected to effect a phase shift in accordance with the impedance thereof.
  • the control signals are different in offset and wave shape in order to produce different phase shifts in the right and left channels, creating a pleasing acoustical effect as will be explained.
  • switching circuit 60 passes the signal corresponding to the complex voicing to a line 98, forming one input of an accompaniment complex phase splitter 100.
  • phase splitter 100 the complex voicing signal is broken down into two signals, one in phase with the incoming signal and having a wave shape identical thereto, and another 180 out of phase with the incoming signal, but otherwise having an identical wave shape.
  • the in phase signal is coupled along an output line 102 to the left channel phase splitter 80.
  • the phase inverted signal is coupled along an output line 104 to the right channel phase shifter 78. Thereafter, the operation is the same as previously described, except that the input waveform to the pair of phase shifters is 180 degress out of phase.
  • phase splitter 100 the accompaniment signal is split into two isolated signals having waveforms similar to the input waveform. Unlike the complex signal, the phase splitter 100 does not invert the phase of one of the output signals. Hence, the signals transmitted via lines 102 and 104 to their respective phase shifters are both in phase with the input signal representing the accompaniment voice.
  • the switching circuit 60 is set appropriately to pass the violin signal along a line 108 and then via line 102 to only the left channel phase shifter 80.
  • the violin voicing is isolated and confined to only the left channel.
  • the left channel phase shifter then processes the incoming violin voicing signal in the same manner as previously described.
  • tremulant effects can be obtained, as described above.
  • the applicants system allows a tremulant effect tailored to the particular voicing.
  • this tailoring or custom tremulant effect has not been possible with prior tremulant systems of the phase shift type, due to the inability to interconnect the phase shifting networks in a variety of configurations of the type described above. Since the tibia voicing, for example, is close to being a pure sine wave having little harmonic content, it can be subjected to more phase shift without production of an unpleasant sound.
  • the violin voicing is processed with phase shifting in only the left channel, creating still another tremulant effect. This versatility of creating a plurality of tremulant effects in a single system is a significant advancement over prior tremulant systems.
  • FIG. 2 the switching circuit 60 and the accompaniment complex phase splitter 100 are shown in detail.
  • the right phase shifter 78 and the left phase shifter 80 and the circuitry associated therewith, are illustrated in more detail but in block diagram form.
  • phase splitter 100 it will be assumed that the voicing circuit 34 of FIG. 1 has been set to pass a complex voicing on the solo manual. In such a case, a signal is present on line 54. For simplicity, it will be assumed that no signals are present on lines 52, 53 and 55. Also, it will be assumed that a switch in circuit 60 is preset as shown in the solid line, such that the complex voicing signal is transmitted to a line 122. The signal then passes through an appropriate input network to the base of a transistor 124.
  • the transistor 124 has a pair of outputs, one output occurring at its collector electrode 126 and the RC network to line 104 which injects the signal at the input of the second stage 78b of the right phase shifter formed by cascaded stages 78a and 78b.
  • the signal appearing at emitter 127 is in phase with the input signal applied to line 122.
  • This signal is coupled via a line 130 to the emitter of a transistor 132. Since the signal on line 130 is emitter coupled to transistor 132, the signal appearing at a collector electrode 134 of transistor 132 is in phase with the signal on line 122.
  • This in phase signal appearing at collector 134 is capacitor coupled to line 102 for transmission to the input of a second stage 80b of the left phase shifter, consisting of cascaded stages 80a and 80b.
  • a solo complex signal is passed through splitter 100, two output signals are produced on lines 104 and 102.
  • the signal on line 102 is in phase and identical with the input signal (except for amplification), and the other signal on line 104 is 180 out of phase with the input signal, but otherwise identical thereto (except for amplification).
  • both the switch 120 and a switch 140 will be in the solid line positions shown in FIG. 2.
  • the signal on line 122 is processed exactly as previously described.
  • the accompaniment signal is transmitted along a line 142 to a base electrode of a transistor 144.
  • the transistor stage 144 is used in the case of the accompaniment signal to lower its impedance in order to make it possible to drive the emitter input of transistor 126 (right output stage) and the emitter input of transistor 132 (left output stage).
  • the accompaniment signal is RC coupled to the line 130, and then injected into emitter 127 of transistor 124.
  • the accompaniment signal mixes with the solo complex signal in transistor 124 to give the right channel output.
  • the accompaniment voicing signal is fed to the emitter of transistor 132 wherein it mixes with the solo complex signal to give the left channel output.
  • both the right channel and left channel outputs are in phase with the input. This is because, unlike the solo complex voice, it has been determined empirically that the most pleasing tremulant effect to which the accompaniment complex voice can be subjected results if both right and left channel outputs are fed in phase to the phase shifters.
  • Each phase shifter circuit 78 and 80 comprises two stages, labeled a and b. Each stage is capable of producing a dynamic phase shift of almost 360". Hence, the maximum obtainable phase shift using both stages is about 720.
  • Both the solo complex and accompaniment complex voices are coupled to only the final stage of each phase shifting circuit, and thus are subjected to slightly less than 360 of dynamic phase shift. The reason is as follows. Any complex voice contains a large harmonic content. In the phase shift circuitry, higher frequencies are subject to greater phase shifts, due to the RL circuit being utilized. When a complex voice is processed by the phase shift circuit, the higher harmonics receive more phase shift than the lower harmonics. This results in a rather unpleasant musical tone if the complex signal is subjected to too much phase shift. It has been found empirically that a 360 phase shift gives a good tremulant to complex tones, without producing discordinant effects due to more extreme shifting 0 higher harmonics.
  • the base of transistor 132 is AC coupled by a capacitor 150 to a source of reference potential or ground 152, making it a common base configuration.
  • This configuration has good output to input isolation characteristics, and thus prevents channel cross-talk between the left and right channels.
  • the tremulant effect produced by the present invention would be substantially destroyed if these channels were not properly isolated. Failure to electrically isolate lines 102 and 104 from each other would result in a signal path connecting the outputs of the first stages of the left and right phase shifters. If such were the case, any output from the two stages would be electrically mixed. This would destroy the intended effect of these two stages, since the tremulant effect of the present invention is realized when the output of two separate channels are acoustically mixed in space.
  • switch 140 is placed in the dotted line position and the signal on line will be passed via line 68 to preamplifier 62.
  • a switch 160 is set as shown by the solid line in FIG. 2.
  • the violin voicing signal is then transmitted along line 35 where it is injected via an RC network directly into line 102.
  • violin voices are preferred in only the left channel.
  • the switch 160 is set to the dotted line position v which transmits the signal on line 53 to the line 65.
  • the violin voicing signal is transmitted directly via line to the left channel preamplifier 66.
  • the switch 170 is set as shown in solid lines.
  • the tibia voicing signal is then translated to line and along lines 75a and 75b into the first phase shift stage 78a of the right channel and the first phase shift stage a of the left channel.
  • the tibia voicing signal is not processed by the complex phase splitter 100. With the tibia voicing signal, it is not necessary to split the signal into two isolated channels to prevent cross coupling, since the signal is injected at the first stage of each phase shifter, rather than the final stage as in the case of complex signals. Once the signals are injected, they proceed independently in the two separate channels.
  • tibia signal is subjected to two stages of phase shift in both the right and left channels; that is, approximately 720.
  • Such signal processing is desirable musically since the tibia voice is almost a pure sine wave; that is, it contains very little higher harmonic content.
  • phase shift the signal it is possible to phase shift the signal to a larger degree because the absence of higher harmonics prevents a discordinant sound even though large phase shift is utilized.
  • the large phase shift is desirable since it results in a very deep tremulant effect, which is especially pleasing on a tibia voice.
  • two stages of phase shift are utilized. Once the tibia voicing signals have passed through the right and left channel of phase shifting circuitry, they are applied separately via lines 82 and 84 to the right channel preamplifier 72 and the left channel preamplifier 66, respectively.
  • switch 170 is placed in the dotted line position and the tibia voicing signal is passed along line 68 to preamplifier 62.
  • phase shifting circuitry and associated stages
  • the electrical phases of the left and right channels must by cyclically advanced and retarded at a rate of approximately 6.7 cycles per second.
  • the electrical phases of signals passing through the right and left channels can be rotated throughout almost 360 in each of the pair of cascaded stages in both the left and right phase shifters.
  • phase shifting circuitry of the present invention provides a more pleasing tremulant effect than prior art phase shifting, in that it dynamically shifts the phase of lower frequency harmonies less than upper frequency harmonics. This results in what might be termed a constant percentage frequency deviation, which is highly desirable for the following reason. If low frequency harmonics of a musical signal (for example those below 200 Hz) are dynamically phase shifted through a significant number of degrees (say approximately 720) at the rate of 6.7 Hz, the perceived variation in frequency due to the Doppler effect is quite extreme. This result occurs because the number of cycles which the frequency deviates above and below the nominal frequency is dependent on the tremulant rate and the number of degrees of dynamic phase shift.
  • phase shifters of the subject invention effectuate this in a manner to be explained below.
  • a single light bulb 200 illuminates a light dependent resistor 202. If an AC signal is applied via a line 204 to the base electrode of a transistor 206, the signal at a collector electrode 208 of the transistor 206 will be 180 out-of-phase with respect to the applied signal on line 204. Furthermore, the signal at an emitter electrode 210 of the transistor 206 is inphase with the appied signal. Thus, two outputs are provided which are 180 out-of-phase.
  • the collector electrode 208 is coupled through an inductor 212 to an output line connected to ajunction 214 of inductor 212 and the light dependent resistor 202.
  • the light dependent resistor (LDR) 202 receives no light, and its resistance is high. It will be assumed that LDR 202 has an infinite impedance at a no light condition. In this case, inductor 212 is unloaded and thus has no AC current flowing therethrough. The output is a shifted signal on line 214 which is in-phase with the signal on collector 208, which in turn is 180 out-of-phase with the input signal on line 204. When the light bulb 200 is energized and it begins to illuminate, a point is reached at which the resistance of LDR 202 is equal to the inductive reactance of inductor 212.
  • inductor 212 and LDR 202 have a minimum resistance and the in-phase component at the emitter 210 predominates on output line 214.
  • the output on line 214 will be in-phase with the input on line 204.
  • the voltage on line 214 again goes l out of phase with the input on line 204.
  • the phase of the signal on line 214 is progressively advanced and retarded with respect to the input on line 204.
  • phase shifting circuit in FIG. 4 makes use of an inductor 212, it is obvious that a capacitive element could be substituted therefor. Should such be done, the direction of the phase shift, as lamp 200 is alternately illuminated and darkened, would be the opposite of that resulting when an inductive element is utilized.
  • capacitor 400 is included in the phase shifting circuitry.
  • Capacitor 400 forms a series resonant circuit with inductor 212.
  • the effect of capacitor 400 will predominate, and the phase shift circuitry will operate in a capacitive mode.
  • the phase shift circuitry operates in an inductive mode.
  • capacitor 400 has a value of 10 microfarads and inductor 212 has a value of 0.350 henries.
  • phase shifter just described is followed by a phase inverter utilizing a Darlington amplifier 220,
  • the second phase shifter is similar to the first described phase shifter, and includes a capacitor 402 in series with inductor 222.
  • a series resonant circuit is formed by capacitor 402 and inductor 222, which connects to the collector electrode of the Darlington amplifier 220.
  • LDR 224 couples to the emitter of the Darlington amplifier 220, and is actuated by lamp 200.
  • capacitor 402 has a value of 40 microfarads and inductor 222 has a value of 0.350 henries, giving a series resonant frequency of 42 Hz.
  • phase shifter applied signals having a frequency below 42 Hz will be dynamically phase shifted in the same direction as signals having a frequency below 84 Hz in the first portion of this phase shifter.
  • Applied signals with frequencies between 42 Hz and 84 Hz will be dynamically phase shifted in a direction opposite to that effected in the first phase shift circuit.
  • Signals with frequencies above 84 Hz will of course be dynamically phase shifted in the same direction in both phase shifters.
  • the output of the second phase shifter is applied to output transistor 226 prior to introduction into the second stage of the right phase shifter.
  • the third and fourth phase shifters which comprise the second stage of right phase shifter 78b operate in a manner similar to the first and second phase shifters in the first stage of the right phase shifter.
  • capacitor 404 has a value of 2 microfarads and inductor 406 has a value of 0.350 henries, resulting in a series resonant frequency of 190 Hz.
  • Capacitor 408 has a value of microfarads and inductor 410 has a value of 0.350 henries, giving a series resonant frequency of 84 Hz.
  • all signals and frequencies above 190 Hz will be dynamically phase shifted in the same direction by both phase shifters.
  • All signals with frequencies below 84 Hz will also be dynamically phase shifted in the same direction, but this direction will be opposite to that for signals having frequencies above 190 Hz.
  • the dynamic phase shift direction in the first phase shifter will be opposite from that of the second phase shifter.
  • the net effect of selecting the resonant frequencies of each of the four phase shifters as specified above is to lessen the dynamic phase shift for signals having frequencies below 190 Hz.
  • a 50 Hz signal will be dynamically phase shifted in opposite direction by the first and second phase shifters. This will result in a partial cancellation of the phase shift effect, since the resultant phase shift will be the difference of the individual dynamic phase shifts.
  • the phase shift direction for the 50 Hz signal will be the same, and thus the total phase shift will be the sum of the two individual dynamic phase shifts.
  • the left phase shifter, first and second stages is identical to the right phase shifter, first and second stages. Hence no detail description of the left channel phase shift circuitry is necessary.
  • a signal applied at line a or 75b thus passes through both the first and second stages of their respective phase shifters to provide about 710 of electrical rotating phase shift. If the signal is inserted only into the second stage b of its respective channel phase shifter, as occurs with signals applied to lines 104 and 102, only about 355 degrees of electrical rotating phase shift is provided. As previously noted, only the tibia voicing signal is subjected to the full 710 of phase shift, resulting in a desirable deeper tremulant.
  • lamp 200 To effectuate a smooth advancement and retardation of phase by the right channel phase shifter, lamp 200 must be cyclically driven from a darkened to a lightened condition.
  • the energization of the lamps for the right and left channels is controlled initially by a tremulant oscillator which provides a 6.7 Hertz signal to a tremulant modulation system.
  • Two out-of-phase outputs are provided from the oscillator 90, shown in detail in FIG. 3.
  • the tremulant oscillator 90 includes transistors 250, 252 and 254.
  • transistor 250 When transistor 250 is conducting, positive charging voltage is supplied through resistors 256 and 257 to a capacitor 260. As the voltage on capacitor 260 rises, the collector current of transistor 254 increases accordingly. The voltage on the collector of transistor 254 then drops toward ground potential. As the voltage on the collector goes towards ground, a signal on a line 262 connected to the collector of transis- -tor'254 also goes toward ground, causing the base drive for transistor 252 to drop. This causes transistor 252 to go out of conduction, resulting in a rise in its collector potential. As the potential at the collector of transistor 252 rises, transistor 250 is forced out of conduction.
  • Capacitor 260 then discharges through the resistors 257, 256 and a resistor 264. As the voltage on capacitor 260 decreases, the collector current of transistor 254 decreases thereby causing a rise in its collector voltage. As the voltage on the collector of transistor 254 rises the signal on line 262 increases thereby providing an increased base drive to transistor 252. Thereafter, transistor 250 returns to a conducting state and the oscillation cycle just described begins over again.
  • the oscillation frequency is governed by the RC time constant of the capacitor 260 and the resistors 256,257 and 264.
  • the value of resistor 256 is variable, and is selected to produce an oscillation rate of approximately 6.7 Hertz.
  • a rectangular wave is developed on an output line 270, and another rectangular wave out-of-phase therewith is developed on a line 272. These output lines are coupled to the right channel lamp driver and the left channel lamp driver, respectively.
  • the square wave signal on output line 270 is fed to the double shaper circuit 94.
  • the circuit 94 is used to develop a double frequency pulse which is coupled to only the right phase shifter lamp driver 96.
  • the double shaper acts like a dual switch, one side being responsive to the positive going portion of the input signal, and the other side being responsive to the negative going portion. The outputs of the two sides are then combined to provide a doubled frequency output driving signal.
  • the operation of the double shaper circuit 94 will be described assuming that a positive going rectangular wave is received on line 270.
  • a pair of capacitors 280, 282 differentiate the rectangular pulse to produce positive and negative going pulses as shown at 284.
  • the positive going pulse causes a transistor 286 todeliver an output pulse ona line 287.
  • the negative going pulse causes a transistor 290 to go into conduction, and provide a second pulse on line 287.
  • the combined offset signals to the right lamp driver 96 appear across a resistor 292.
  • the double frequency pulses developed across resistor 292 are depicted by curve 300.
  • a transistor 302 in the right lamp driver 96 is biased into conduction.
  • a cascaded transistor 304 is also biased on.
  • transistor 304 conducts, it supplies current through a line 306 to lamp 200.
  • the illumination level of the lamp 200 is controlled by the waveform 300, FIG. 5A, applied across the resistor 292.
  • the circuit of the left lamp driver 92 is identical to the circuit just described for the right lamp driver 96. However, since no double shaper is interposed between the tremulant oscillator 90 and the lamp driver, the lamp 320 in the left channel phase shifter 80 is not illuminated in the same manner as lamp 200 in the right channel phase shifter 78. Rather, lamp 320 is energized bya signal 322 as shown in FIG. 5B. Thus, the two driving waveforms 300 and 322, shown in composite form in FIG. 5C, are time offset and produce an alternating, or interleaving effect. It has been discovered empirically that a most desirable form of tremulant is produced by the signals shown in FIG. 5.
  • the double-shaped waveform 300 which is applied to the right channel lamp 200, will be considered.
  • the waveform 300 is comprised of a first pulse 330 followed by a second pulse 332. These dual pulses do not cause the lamp 200 to flash twice because of thermal lag inherent in the lamp. Rather, it appears that the first pulse 330 causes preheating of the lamp, so that when pulse 332 is applied, the lamps light output rises faster than would be the case without preheating.
  • pulse 332 returns to zero, the decrease in light output of the bulb does not follow the waveform of the trailing edge of pulse 332 because the light output is decreased in accordance with the thermal lag of the lamp.
  • each LDR in the left channel phase shifter versus time is shown by curve 346 in FIG. SB.
  • the application of a pulse such as that indicated at 322 results in the resistance curve 346 which then causes a frequency deviation in the left channel as shown by curve 350, FIG. 5E.
  • the frequency deviation as shown by curve 344 in FIG. 5D has been found to result in a very desirable tremulant effect.
  • the applicants driving waveforms and circuitry are designed so that there is not a continuous variation in phase as has been typical heretofore. Rather, the frequency deviation of the signal as shown by waveform 344 occurs in spaced time zones, in' that between times t, and t the frequency deviates in a smooth, almost sinusoidal manner below and above the nominal frequency. However, during the period between t, and t the frequency does not deviate, but rather remains substantially at a nominal value. This pause or absence of a continuous frequency deviation is believed to be partially responsible for the improved tremulant effect produced by the present invention.
  • FIG. SF shows the envelope of the beat between the left channel and right channel output signals.
  • the modulation envelope reflects the loudness variations which a listener equidistant from each channel speaker would hear if a 1,000 Hertz sine wave were introduced into both the left and right channels, where each would be continuously dynamically phase shifted.
  • the improvement in the tremulant effect results from various contributions of the circuitry and waveforms previously described As seen in FIGS. 5D and 5B, the frequency deviation in the right channel, curve 344, does not occur during the same time period as the frequency deviation in the left channel, curve 350.
  • the right and left channel deviations in frequency alternate or interleave with each other since the major frequency deviation period in the right channel (the time period between t, to t,) is delayed with regard to that of the left channel major frequency deviation period.
  • the resulting acoustical effect is a more or less continual reinforcement and cancellation of waveforms, thereby giving a desired amplitude variation. It is believed that the alternation of the frequency deviation periods further contributes to the improved tremulant effect.
  • the resulting pleasing tremulant effect is available on most of the custom tremulant effects which can be realized by the system through the previously described selective combination of phase shifting circuits.
  • a system for producing different cyclical variations in electrical signals representing different musical instruments comprising:
  • phase shift stages each including variable means controllable to vary the phase shift of the corresponding phase shift stage
  • an oscillator coupled to said variable means for cyclically varying the phase shift produced by each of the plurality of phase shift stages
  • switch means for coupling one of said sources to said input junction and another of said sources to said intermediate junction whereby some of said plurality of phase shift stages are used in common by different sources corresponding to different musical instruments.
  • the system of claim 1 including a first channel for processing and a first reproducer for reproducing said electrical signals and a second channel for processing and a second reproducer for reproducing said electrical signals, the acoustical interaction of the electrical signals reprodued by the first and second reproducers producing a tremulant cyclical variation,
  • said two phase shift stages being located in said first channel
  • said plurality of phase shift stages includes a third phase shift stage responsive to third variable means for producing a third phase shift deviation and a fourth phase shift stage responsive to fourth variable means for producing a fourth phase shift deviation, said third and fourth phase shift stages being located in said second channel,
  • said circuit interconnecting said third and fourth phase shift stages in series to produce in an electrical signal coupled to an input junction a total phase shift approximately equal to the sum of the third and fourth phase shift deviations, the series interconnection including an intermediate junction between said third and fourth phase shift stages, and
  • said switch means further couples said one source and said another source to different of said junctions located in said second channel.
  • circuit includes inversion means for producing a phase shift of approximately 180", and said switch means interconnect said inversion means between said another source and one of said intermediate junctions to thereby input to the last phase shift stages in the first and second channels a pair of electrical signals which are out of phase.
  • circuit includes isolation means for splitting the signal from said another source into two in-phase portions, and said switch means interconnects said isolation means with said intermediate junctions to thereby input to the last phase shift stages in the first and second channels a pair of in phase signals without cross-coupling said first and second channels.
  • phase shift stages includes a first stage located in said first channel and a corresponding second stage located in said second channel, each stage including a variable means controllable to vary the phase shift thereof, and
  • said oscillator includes means for generating different control signals and means for coupling said different control signals to the variable means in the first and second stages to produce different phase shift deviations in the electrical signals processed by the first and second channels.
  • a system for producing a cyclical variation in an electrical signal representing a musical voice comprising:
  • a first channel coupled to said source for processing said electrial signal, including a first phase shift stage having a first variable means controllable to vary the phase shift deviation produced in the first channel;
  • a first audio reproducer coupled to said first channel for reproducing the processed electrical signal
  • a second channel coupled to said source for processing said electrial signal, including a second phase shift stage having a second variable means controllable to vary'the phase shift deviation produced in the second channel;
  • a second audio reproducer coupled to said second channel for reproducing the processed electrical signal
  • an oscillator for generating a pair of control waveforms having cyclical variations, including a wave shaper for altering the shape of one of the control waveforms and means for individually coupling said pair of control waveforms to the first and second variable means, respectively, to produce different phase shift deviations in said first and second channels;
  • said first and second audio reproducers coupled to said first and second channels reproduce said cyclical variation in response to an acoustical interaction produced by the difference in phase shift deviation between the electrical signals processed in said first and second channels.
  • said first variable means is responsive to the one of said control waveforms coupled thereto for producing recurring periods of phase shift, each recurring period comprising a first time portion which controls said first phase shift stage to produce a substantially continuous frequency deviation and a second time portion which controls said first phase shift stage to produce substantially no frequency deviation.
  • each of said variable means comprises a light responsive impedance having an impedance value corresponding to the light energy impinging thereon, a first lamp for controlling the amount oflight energy impinging on the impedance in said first channel, a second lamp for controlling the amount of light energy impinging on the impedance in said second channel, and said individually coupling means coupling the pair of control waveforms to said first and second lamps, respectively.
  • said wave shaper comprises a wave doubler for causing one control waveform to comprise a pair of pulses, the other control waveform comprising a single pulse for each pair of pulses produced by the wave doubler.
  • each of said phase shift stages includes a transistor having first and second output electrodes and a control electrode, means coupling the control electrode to the electrical signal being processed, a reactance coupled between said first output electrode and ajunction, and said light responsive impedance being coupled between said second output electrode and said junction to cause the electrical signal at the junction to have a phase shift corresponding to the impedance value of said impedance.
  • each of the first phase shift stage and the second phase shift stage include a plurality of transistors, reactances and light responsive impedances, the junction associated with the first connected transistor in each phase shift stage being in series with the control electrode of the next transistor, and the lamp for each channel causes substantially the same light energy to simultaneously impinge all of the light responsive impedances in the associated channel.

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  • Engineering & Computer Science (AREA)
  • Acoustics & Sound (AREA)
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  • Electrophonic Musical Instruments (AREA)
US00244573A 1972-04-17 1972-04-17 Electronic musical instrument with phase shift tremulant system Expired - Lifetime US3778525A (en)

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Cited By (4)

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Publication number Priority date Publication date Assignee Title
US5225619A (en) * 1990-11-09 1993-07-06 Rodgers Instrument Corporation Method and apparatus for randomly reading waveform segments from a memory
US6259006B1 (en) * 1996-08-30 2001-07-10 Raoul Parienti Portable foldable electronic piano
US20080264242A1 (en) * 2007-04-12 2008-10-30 Hiromi Murakami Phase shifting device in electronic musical instrument
US20110317841A1 (en) * 2010-06-25 2011-12-29 Lloyd Trammell Method and device for optimizing audio quality

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US3378623A (en) * 1965-05-07 1968-04-16 Seeburg Corp Tremolo-vibrato circuitry for use with a simulated moving sound source or the like
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US3418418A (en) * 1964-05-25 1968-12-24 Wilder Dallas Richard Phase shift vibrato circuit using light dependent resistors and an indicating lamp
US3516318A (en) * 1968-01-02 1970-06-23 Baldwin Co D H Frequency changer employing opto-electronics
US3524376A (en) * 1965-10-20 1970-08-18 Solomon Heytow Vibrato circuit utilizing light-sensitive resistors and organ embodying same
US3609204A (en) * 1969-10-06 1971-09-28 Richard H Peterson Vibrato system for electrical musical instrument
US3609205A (en) * 1970-05-15 1971-09-28 Wurtilzer Co The Electronic musical instrument with phase shift vibrato
US3644657A (en) * 1969-10-20 1972-02-22 Francis A Miller Electronic audiofrequency modulation system and method

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Publication number Priority date Publication date Assignee Title
US2892372A (en) * 1953-07-16 1959-06-30 Wurlitzer Co Organ tremulant
US2892373A (en) * 1955-05-19 1959-06-30 Wurlitzer Co Multiple tremulant for treble tones in electronic musical instruments
US3004459A (en) * 1956-12-31 1961-10-17 Baldwin Piano Co Modulation system
US3004460A (en) * 1956-12-31 1961-10-17 Baldwin Piano Co Audio modulation system
US3007361A (en) * 1956-12-31 1961-11-07 Baldwin Piano Co Multiple vibrato system
US3160695A (en) * 1959-03-02 1964-12-08 Don L Bonham Electrical music system
US3336432A (en) * 1964-03-04 1967-08-15 Hurvitz Hyman Tone generator with directivity cues
US3418418A (en) * 1964-05-25 1968-12-24 Wilder Dallas Richard Phase shift vibrato circuit using light dependent resistors and an indicating lamp
US3398230A (en) * 1965-01-13 1968-08-20 Seeburg Corp Sequential connction of speakers for moving sound source simulation or the like
US3388257A (en) * 1965-01-14 1968-06-11 Ampeg Company Inc System for introducing tremolo and vibrato into audio frequency signals
US3378623A (en) * 1965-05-07 1968-04-16 Seeburg Corp Tremolo-vibrato circuitry for use with a simulated moving sound source or the like
US3524376A (en) * 1965-10-20 1970-08-18 Solomon Heytow Vibrato circuit utilizing light-sensitive resistors and organ embodying same
US3516318A (en) * 1968-01-02 1970-06-23 Baldwin Co D H Frequency changer employing opto-electronics
US3609204A (en) * 1969-10-06 1971-09-28 Richard H Peterson Vibrato system for electrical musical instrument
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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5225619A (en) * 1990-11-09 1993-07-06 Rodgers Instrument Corporation Method and apparatus for randomly reading waveform segments from a memory
US6259006B1 (en) * 1996-08-30 2001-07-10 Raoul Parienti Portable foldable electronic piano
US20080264242A1 (en) * 2007-04-12 2008-10-30 Hiromi Murakami Phase shifting device in electronic musical instrument
US20110317841A1 (en) * 2010-06-25 2011-12-29 Lloyd Trammell Method and device for optimizing audio quality
WO2011163642A3 (en) * 2010-06-25 2014-03-20 Max Sound Corporation Method and device for optimizing audio quality

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DE2319520A1 (de) 1973-10-31
AU5427673A (en) 1974-10-10
IT980231B (it) 1974-09-30
AU474600B2 (en) 1976-07-29
GB1417254A (en) 1975-12-10
NL7305293A (show.php) 1973-10-19

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