Theremin U.S. Patent


METHOD OF AND APPARATUS FOR THE GENERATION OF SOUNDS

Application filed December 5, 1925, Serial No. 73,529, and in GermanyDecember 8, 1924.

This invention relates to sound generating apparatus or instruments of thetype embodying an electrical vibrating system. It aims to provide a novelmethod of and means for producing sounds in musical tones or notes of variablepitch, volume and timbre in realistic imitation of the human voice and variousknown musical instruments. One object of the invention is to provide a simpleand inexpensive instrument capable of producing musical tones according to themethod embodying the same, the pitch, volume and timbre of which sounds may bevaried over a wide range, and with delicate graduations.

An instrument embodying the invention comprises a sound reproducer. such asa telephone receiver or loud-speaker, connected to an oscillating systemadapted to be controlled or affected by an object or objects, such as the handsor fingers of an operator held in relative position in proximity to an elementof the system. For example, an electrical oscillating system includingoscillator tubes of the electro-ionic type may be employed, and the circuits ofthe system may be so correlated that the frequency or frequencies of theelectrical oscillations will vary in accordance with the variations in theelectrical capacity or other characteristic of the controlling circuit causedby the movements of external objects, such as an operators hand or fingers asabove stated. The operator’s hands, or the objects moved by him are notrequired to make physical contact with the instrument, but if the instrument isarranged to permit such contact, the generation or production and control ofthe sound is not effected directly thereby as is the case with the ordinarymusical instruments.

In order to generate clear sound or musical tones and permit ready controlthereof, a plurality of oscillators are employed, having a frequency above theaudible range but interacting with each other to produce interference orbeat_notes of audible frequency. The frequency of one or more of theoscillators is controllable by the operator to produce beat-notes of thedesired pitch. The apparatus in preferred form also embodies means forcontrolling the volume and timbre of the music.

The improved method and means of this invention for producing sound ormusical tones possess great advantages over ordinary musical instruments of theprior art. Apart from the simplicity in construction and operation of aninstrument embodying the invention, it is capable of producing clear and puremusical tones in realistic imitation of a known instrument, such as the violinfor example, and may be so constructed that the characteristics of the sound ormusic produced thereby may be changed as desired in imitation of various otherinstruments, whereas the ordinary musical instrument, such as the violin,produces sound tones of fixed and well-known characteristics. The instrument isnot limited, however, to the production of music but may be employed togenerate sounds or operate signals for various purposes.

Other objects and advantages of the invention, particularly with referenceto electrical elements and circuits and their arrangements in systems forsecuring various results in different constructional embodiments which havebeen devised, will appear from the following description considered inconnection with the accompanying drawings in which are shown several modifiedforms of the invention. Various practical embodiments of the invention areherein-after described in order to make a full and complete disclosure, but theinvention obviously is not limited to the specific arrangements shown and it isto be understood that no limitations thereon are intended beyond those setforth in the appended claims.

Referring to the drawings,

Fig. 1 is a diagrammatic view of electrical circuits and apparatus arrangedin accordance with the invention for the production of a single tone ofvariable pitch

Fig. 1a is a similar view of a modification;

Fig. 2 is a similar view of a further modification embodying amplifiers;

Fig. 3 is a diagrammatic view of a modified form of reproducer circuit;

Figs. 4 and 5 are diagrammatic views of different form of control circuits;

Fig. 6 is a diagrammatic view of a system for producing two tones;

Figs. 7 and 8 are similar views of systems for producing four tones;


Figs. 9 to 14 illustrate means for regulating the volume of the sounds;

Figs. 15 to 18 illustrate systems for switching the tone on and off by meansof a wire connection;

Fig. 19 shows a system for effecting the same result by a modified form ofcontrol;

Figs. 20 to 22 show systems for eliminating the natural oscillations;

Figs. 23 to 26 illustrate systems for regulating the timbre of the sound ortone; and

Fig. 27 illustrates a complete system for simultaneously producing aplurality of sound or musical tones on the same or different pitches, andembodying means for controlling the characteristics thereof.

A preferred form of instrument embodying the invention and operableaccording to the method embodying the same, comprises the following elements:

I. A control element or electrode with relation to which an object such asthe hands or fingers of an operator are moved to control the pitch andcharacter of the sound tones emitted by the instrument. Said element does notfunction like the antenna in a wireless receiver set or apparatus, i.e., itdoes not receive or detect radiant energy transmitted from a distanttransmitting station, but, has a novel and radically different function as willappear from the detailed description in connection with the various circuitarrangements illustrated in the drawings.

II. Oscillating circuits adapted to produce one or more beat-notes ofaudible frequency.

Means for regulating the volume of sound tones.

IV. Means for switching individual sound tones on and off as desired.

V. Means for controlling the timbre of the sound tones.

VI.- Means for eliminating or nullifying the natural oscillations of theamplifier or reproducer to prevent the production of undesirable noises ordistortion of the sound tones.

In broad aspect, the means of the invention comprises an oscillating systemcapable of producing audible sound tones and adapted to be influenced oraffected by an object objects, such as the hands or fingers of an operatormoved in proximitive relation to an element thereof, together with a soundreproducer operatively connected to said system. Stated differently, theinvention embodies a method and means for producing oscillating system in whichthe period is varied and the characteristical sound emission from which ischanged by the movement of an object or objects in proximitive relation to anelement thereof. The said system may be electrical and so arranged thatmovement of an operator’s hands or fingers will change the electricalcharacteristic thereof such as the electrostatic capacity between, certainelements which determine the period of the oscillator, but while such a systemis disclosed and hereinafter described in detail it is obvious that other typesof oscillating systems and other means of control may be employed to accomplishthe same result.

In Fig. 1 of the accompanying drawings a system is shown embodying anelectrode or control-element 1 operatively connected to an electricaloscillating system and an electrical sound-reproducer. The electrode orcontrol-element is in this instance connected to an oscillator 2 of theelectro-ionic type and to a resonant circuit 3 which is traversed by anoscillatory current, the frequency of which depends upon the constants of thecircuit and of the circuits conductively or inductively related thereto. Theoscillator 2 is represented as of the filamentary-cathode type operating by anelectron discharge from the cathode, but other forms of oscillators may be usedand are intended to be included by the phrase “electro-ionic”.

A second oscillator 4 is shown connected to the circuit 3, said lastmentioned oscillator with the oscillator 2 being arranged to control a thirdelectro-ionic tube 5 through coils 6 and 7 which are inductively related to thetwo oscillators. A condenser 8 is represented as interposed between the coils 6and 7 and the tube 5, and a grid-leak resistance 9 is shown connected betweenthe grid terminal of said condenser and the cathode circuit. The output circuitof the tube 5 is connected through the audio transformer 10 to a tonereproducer or loudspeaker 11. The tubes 2, 4, and 5 are connected to a suitablesource of current, such as a battery, as indicated at 12.

The oscillating frequencies of the oscillators 2 and 4 are preferably abovethe range of audibility, but are nearly the same so that the interferencefrequency produced in the ciruit of the tube 5 will be relatively low andproduce a beat-note of audible pitch in the loudspeaker 11. The frequencies ofvibrations in the circuit of the tube 5 may be called audible frequencies asthey will have substantially the same number of vibrations as the vibrations ofan audible sound wave. The pitch of this note, and the presence and strength ofthe overtones are controlled by selection and arrangement of the condensers,inductances and other elements of the circuits in a known manner.

The frequencies of the oscillators 2 and 4 may be of the order of 500,000cycles per second, the precise frequency being so chosen that no interferencewith radio broadcast reception is produced. The values of inductance andcapacity employed in the oscillating circuit are selected in accordance with


well-known principles to provide the desired frequencies and the variationof the capacity of the variable oscillator is effected by the change ofcapacity of the control electrode, which change in capacity in instruments thathave been built is of the order of 10e-8 micro-farads. It will be understoodthat this change of capacity effected by external control is so correlated withthe capacity in the oscillator circuit, that the resultant range of pitch ofthe musical instrument covers several octaves.

The sound generated in and emitted through the loud-speaker is alsocontrolled by the movement of an object or objects, such as an operator’sfingers in proximitive relation to the electrode or control-element 1 which isconnected to the oscillating circuit 3 and to the grid of the oscillator 2. Theelectrical characteristics of said control element influence the period orfrequency of the oscillator 2 and the character of the beat-note in thereproducer. As the operator’s fingers are moved in suitable relationship withsaid control element, the pitch of the beat-note in the reproducer 11 isvaried, and continuous variations may be produced with most delicategraduations by the continuous movement of the fingers.

This control is primarily the result of changes occurring in theelectrostatic capacity between the control element and the ground potential orbetween the control element and other elements of the circuits. Therefore, itis obvious that other objects than the operator’s fingers would be operable tovary the tone produced. Furthermore, it will be appreciated that the amount anddirection of the controlling movement will depend somewhat upon the dimensionsand arrangement of the control element which may be of such character thatmovement of the fingers to the extent required to play any ordinary instrumentsuch as the violin, will produce a corresponding effect and note change in thepresent sound generating instrument, so that one who has learned to play theviolin or some other instrument will have little difficulty in playing thepresent instrument.

The system shown in Fig. la is similar to that shown in Fig. 1, except, thatcoupling condensers 13 and 14 are substituted for the inductive couplingbetween the circuits of the latter. A great many other modifications of thiskind may be made in the arrangement of the electrical oscillating systemwithout departing from the scope of the invention.

In Fig. 2 a further modification including amplifiers is shown.Amplification of the electrical currents may be effected in various ways, butit is preferable to use an arrangement in which there is a minimum distortionof the sound tones. It is also generally preferable to amplify each of thehigh-frequency currents separately, rather than the low-frequency beat-note,although a low-frequency amplifier may also be utilized.

Referring to Fig. 2, an electrode or control-element 15 is shown connectedto an oscillator 16, the output circuit of which is connected to an amplifier17, preferably of the electro-ionic type as represented. A second or auxiliaryoscillator 18 is shown connected to a second amplifier 19. The output circuitsof said amplifiers 17 and 19 are connected to the input electrode or grid of anelectro-ionic tube 20, whereby a beat-note of audible frequency is produced inthe output circuit thereof. The output circuit of the tube 20 Is connectedthrough a transformer 21 and through an audio-frequency amplifier 22 to aloud-speaker 23. An anode battery 25 is connected in parallel to all of theelectro-ionic tubes in the usual manner. A non-inductive resistance 24 isconnected between the grid and cathode of the tube 20 and a condenser 26 isconnected between the grid of tube 20 and the anode of the amplifier tube 19. Asecond condenser 27 is connected between the condenser 26 and the battery 25.This condenser is preferably variable as indicated. Condensers 28 and 29corresponding with the condensers 26 and 27 are also provided in connectionwith the amplifier 17.

In the arrangement just described, the high-frequency oscillations of thecontrollable oscillator 16 and the auxiliary oscillator 18 are amplifiedseparately, and then the combined oscillations are amplified together.

In Fig. 3, a further modification of the amplifier is shown. The left handportion of Fig. 3 is the same as Fig. 2 as fas as the line III-Ill. Theamplifier 22 is shown connected with the transformer 21 to which are connectedfour amplifiers 31, 32, 33 and 34, the latter being inductively connected withthe amplifier 22 through the transformer 30. In this instance, amplifiers 32,33, and 34 are connected in parallel to obtain a direct-currentintensification, and said three amplifiers are connected in group to the fourthamplifier 31. The tone reproducer 23 and the anode battery 25 are connected asin Fig. 2. This arrangement is suitable especially by reason of its highefficiency for comparatively low frequencies, particularly for bass tones.

The oscillations of the controllable oscillator and the fixed oscillator aremade independent of each other, and for such reason the amplification of eachcurrent takes place separately. Each oscillation is thus first amplifiedindividually and then only is amplification of the combined oscillationseffected.

The connection of the control element to the oscillating system may bemodified variously while still obtaining the desired results.


A plurality of electrodes may be employed to produce a plurality of soundtones simultaneously from the same object moved in relation thereto. Forexample, two straight parallel conductors may be employed If the object movedrelatively thereto is equi-distant from both conductors, then the two tonesproduced therethrough will be the same if other conditions are equal. As themoving object approaches nearer to one conductor than the other, the pitch ofone tone will increase while that of the other will decrease. Three or moreconductors may be provided, preferably in symmetrical arrangement, or aplurality of symmetrical groups of conductors may be arranged and controlled bydifferent objects or fingers of the operator’s hand.

Connection of the conductor or conductors to the oscillator should be suchthat changes in capacity will produce a considerable change in the oscillator.Connection may be made either to the grid or anode circuit of the oscillator,the most suitable connections being illustrated in the drawings.

In Fig. 4 a connection of the control element to the anode circuit is shown.With the controllable oscillator 73 is associated an oscillating circuitincluding inductances 74 and 75 and condensers 76 and 77. Energy is supplied tothe oscillator by an anode battery indicated diagrammatically at 78. Thecontrol element 79 may be connected with plate circuit as shown in full linesat 79, or with the grid circuit as shown in dotted lines at 79′. It makeslittle difference whether the control element is connected the one way or theother provided conditions are otherwise equal. But if this is not the case thecontrol element is connected preferably to the larger inductance. Thesensitiveness of the system may be increased by grounding the circuit at 80,but as a rule this connection is not required in view of large counterpoises ofthe oscillating circuit.

In the system illustrated in Fig. 5, the control element 81 is inductivelycoupled with the oscillator 83 through the medium of a coil 82. An adjustablecondenser 84 is shown arranged in the oscillating circuit of the oscillator 83by which the control circuit is tuned. In this system, by reason of thecounting coil 82, the control element may be at a somewhat greater distancefrom the oscillator 83.

In order to produce a plurality of sound or musical tones simultaneously, aplurality of interfering oscillators may be employed. For instance, threeoscillators properly arranged will produce two tones, one resulting frominterference between the first and second oscillators and the other resultingfrom interference between the second and third oscillators. In like manner,three tones may be produced by four oscillators and so on.

In Fig. 6 is represented an arrangement for producing two sound tonessimultaneously by the use of three oscillators, each tone being separatelycontrollable. One control electrode 35 is shown associated with an oscillator36 and with a low-frequency detector tube 37. Another control electrode 38 isshown associated with an oscillator 39 and a low frequency detector tube 40.The said detectors 37 and 40 are both responsive to the fixed oscillator 41. Anamplifier 42 responsive to both of the beat-notes or tones is shown connectedthrough a transformer 43 with a sound reproducer 44.

Fig. 7 illustrates a further modification comprising four controlelectrodes, viz 45, 45′, 45″ and 45”’ respectively associated with oscillators46, 47, 48 and 49, whereby four tones may be produced simultaneously. The fouroscillators cooperate with a fixed oscillator 50 and are inductively connectedwith detectors 56, 57. 58 and 59 through coils 51, 52, 53, and 54. Each is alsoconnected with one of the coils 60, 61, 62 and 63 of a transformer. Condensers64, 65, 66 and 67 are connected in parallel with said coils 60, 61, 62 and 63.The neutral points of all four coils are connected with the coupling coil 55 ofa fixed oscillator 50. A secondary coil 68 of the transformer is connected tothe amplifier 69 which operates the reproducer 71 through the transformer 70.

Fig. 8 shows another four-tone system, but in this instance thehigh-frequency alternating potential is supplied directly from the platecircuit. The coupling coils 51, 52, 53, 54 and 55 are eliminated and replacedwith a variable coupling coil 72 which is shown connected to the anode of thefixed oscillator 50 at one end, and to the neutral point of the fourtransformer coils 60, 61, 62 and 63 at the other end. The secondary winding 68of the transformer controls the amplifier 69 from which the combined tones aretransmitted to the reproducer 71 through the transformer 70.

The detectors used in connection with the above systems may be of anysuitable type crystal detectors being considered generally preferable.

For regulating the volume of the sound, the intensity of the current may bevaried and variation of the current intensity may be effected in several ways.

Referring now to Fig. 9, a connection is shown in which the oscillator oramplifier 85 which generates the sound tones actuates the reproducer 86, towhich an adjustable resistance 87 is connected in parallel. The resistance 87is adjusted by means of a pedal or the like, and controls the volume of thesound. The adjustable resistance 87 may


also be connected in series with the reproducer.

Fig. 10 shows a further modification in which an adjustable resistance 88for controlling the volume, varies the cathode current of the amplifier 89,which in turn controls the reproducer 90.

The system illustrated by the diagram of Fig. 11 is similar to that shown inFig. 10, except that the cathode current is regulated inductively from thehi-frequency circuit of the tube 100 in the amplifier, with utilization of agreater or lesser energy absorption in the conductor 92 as determined by itsresonance with the oscillating circuit 91 variable according to the operator’smovement of his fingers or other object with relation to the conductor.

The conductor 92 is connected with a coupling coil 93 which latter isinductively related to a coupling coil 94 connected in series with the couplingcoil 95 for the oscillating circuit 91, and a coupling coil 96 for the cathodeof the direct-current amplifier. Both coupling coils 94 and 95 cooperate sothat maximum energy will be generated when the control circuit and oscillatorcircuits are in resonance.

The conductor 92 is a separate control element for regulating the soundvolume and will be referred to as the “sound-volume” control element orelectrode. Adjustment may be so effected that resonance occurs when thecontrolling object is either nearest to, or altogether removed from thiselectrode. Therefore while one hand of the operator generates the various soundtones in the first or “sound generating” electrode his other hand may regulatethe intensity of the tone at the, second or “sound volume” electrode.

The system in Fig. 11 is intended to be connected with the left-hand end ofthe diagram of Fig. 2, the line III-III in Fig. 11 indicating its point ofconnection with Fig. 2. The amplifier 98 which is also a direct-currentamplifier controls the reproducer 99.

The system shown by the diagrams of Figs. 12, 13 and 14 are similar to thatshown in Fig. 11.

In Fig. 12, the cathode current for the amplifier 97 is generated by directconnection of the transformer 96 with the oscillating circuit 91. In Fig. 13,the resonance transmission of energy to the circuit 102 through the circuit 101is utilized under the influence of the controlling object or its distance fromthe “sound volume” control electrode.

The “sound volume” control electrode 92 is directly connected to the anodeor the circuit 101 of the oscillator 100, and the circuit 102 which is coupledtherewith supplies current to the cathode of the amplifier 97 over the variabletransformer 103.

In Fig. 14, the sound volume is regulated by varying the average gridpotential in one of the amplifiers by means of the non-inductive resistance104, which is also in the anode circuit of the oscillator 98. The circuit ofthe “sound volume” electrode 92 is coupled with the oscillating circuit of thetube 100, which is connected with the non-inductive resistance 104. If a fingeror other object is made to approach the electrode 92 the resonant frequenciesof the electrode circuit and of the oscillating circuit of the tube 100 willvary, whereby a corresponding voltage drop will be produced in the resistance104 which by affecting the tube 98 causes a change in the volume of the sound.

The diagrams of Figs. 9 and 14 are most efficient under normal conditions.

The preferred means for switching the sound tones on and off comprise meansfor controlling the current serving for producing tones in the reproducer.

Fig. 15 shows an ordinary switch 105 in the plate circuit of the amplifierin series with the reproducer 106 as shown in full lines, or in parallel asshown at 105′ in dotted lines.

As shown in Fig. 16, the primary winding of a transformer 107 may beconnected in the plate circuit of the amplifier and the tone producer 108 andthe switch 109 connected in the secondary circuit of the transformer. Thiseliminates the undesirable constant component of the pulsating current throughthe reproducer.

The diagram of Fig. 17 is similar to that of Fig. 16, but the transformer107 is replaced by a choke coil 110 from which a circuit is branched inparallel, the reproducer 111, the switch 112 and the condenser 113 beingconnected in series in this circuit.

In Figs. 18a and 18b, the switch is in the cathode circuit. In Fig. 18a, theswitch 114 controls the current from the filament battery 115 of an amplifier116, in the plate circuit of which the reproducer 117 is arranged. In Fig. 18b,the switch 119 is in a shunt circuit 118 of the cathode heating circuit whichis connected with the filament battery, said battery being in continuousconnection with the filament wire in series with a resistance 121.

In Fig. 19 is illustrated an arrangement for switching the tone on and offby a control analogous to the arrangements for varying the volume of soundshown in Figs. 11 to 14.

The system of Fig.19 is intended to be connected with the system of Fig. 2along the line III-III as in the arrangement 01 Fig. 11. The two direct-currentamplifiers 97 and 98 control the reproducer 99. A third control element 122 isprovided for switching the tones on and off through the medium of the cathodecurrent, and is


operated like the “sound generating” and “sound volume” electrodes. Thecontrol element 122 is coupled with a control circuit by a coil 123, whichcircuit includes coupling coils 124, 125, and 126. The coil 125 is coupled withthe amplifier corresponding with the tube 100 in Fig. 11 and the coil 126 iscoupled with the cathode current of the amplifier 127. Current from the anodebattery 129 flows through a relay 128 which operates a switch 130. The switchcontrols the circuit of the cathode battery 131 for the heater of thedirect-current amplifier 97. By the operator’s movement of his hand or otherobject with relation to the electrode 122, the filament current of theamplifier 97 and consequently the tone is cut on or off.

The systems of Figs. 16 and 17 are considered superior to that of Fig. 15,while the systems of Figs. 18 and 19 are regarded as preferable because theswitching on and off will take place without any noticeable interval.

Elimination or neutralization of the various natural oscillations in theapparatus is desirable to improve the quality of the sound or musical tone andmay be effected through compensation by means of an electric system of the samefrequency and damping as is possessed by the oscillating system, the action ofwhich is to be paralyzed.

In Fig. 20 is shown a reproducer 132 to which is connected a circuit withcorresponding oscillation constants. This circuit comprises the inductance 133,the non-inductive resistance 134 and the condenser 135, which are connected inseries and are variable. The resistance and the inductance in particular, arepreferably variable individually.

As represented in dotted lines in Fig. 20, the arrangement may also be suchthat the circuit of these oscillation constants, comprising the inductance133′, the condenser 135′ and the non-inductive resistance 134′, is connected inparallel with the reproducer 132.

Should natural oscillations of various parts exist, for example, if the hornof the loud-speaker possesses a natural oscillation and the diaphragm of theloudspeaker possesses another natural oscillation, a compensating oscillatingcircuit of the same period is employed for each natural oscillation, thecircuits being connected either in series or in parallel.

Fig. 21 shows such a series connection. Three oscillating circuits 137, 138,139, each of which comprises an inductance, a non-inductive resistance and acondenser, are shown connected to the reproducer 136.

According to Fig. 22 the arrangement may be such that parallel to thereproducer 140 are connected the oscillating circuits 141, 142, 143, eachconsisting of an inductance, a capacitance and a non-inductive resistance.

These means for eliminating the natural oscillations may find generalapplication beyond the example stated above, for instance, in sound amplifiersof any kind or their equivalents.

The variation of the quantitive composition of the over-tones in the soundor musical tones may be effected by various deformations of the primaryalternating current, by utilizing the curved parts of the amplifiercharacteristics.

The composition of the overtones may also be varied by increasing orreducing the overtones of the higher order by inserting oscillating elementscomprising capacitances and inductances of suitable values.

Fig. 23 illustrates such a system of connections. The oscillator oramplifier 144 supplies the transformer 145, the secondary winding of whichcontrols the reproducer 146. A variable inductance 147 with a correspondinglyvariable capacitance 148 are connected in parallel with the reproducer. If theinductance alone is used, the overtone frequencies pass through the reproducer.If the capacitance alone is used, the overtone frequencies pass through thecondensers and do not affect the reproducer. If both the inductance andcapacitance are used together, the correct composition of the overtones isobtained. Instead of the arrangement described, a variable choke coil 149 and avariable condenser 150 may be connected in series with the reproducer 146 asindicated in dotted lines. In this case, the connection 151 is eliminated. Botharrangements may be provided together, but the connection 151 is eliminated inthis case also.

Fig. 24 illustrates a simple expedient for varying the characteristic of oneof the amplifiers for example. The plate potential of the amplifier 152 for thereproducer 153 may be varied by the adjustable resistance 154. The cathodecurrent may be varied by the rheostat 155, or the grid potential by therheostat 156. The connection to the other parts of the system as shown in Fig.2 is effected by the transformer 21. In the selection of such characteristicsas are required for the given proportion of overtones, perfect results may beobtained by the combination of the characteristics of various electro-ionictubes, for instance the parallel connection of tubes with different operatingcharacteristics.

In the diagram of Fig. 25, the transformer 21 which may be connected to thesystem of Fig. 2, controls the grids of four amplifiers 157, 158, 159, and 160.From each plate of said amplifiers, current flows to the reproducer 165 and theanode battery 166 through rheostats 161, 162, and 164, one for each amplifier.One of the rheostats 167, 168, 169 and 170 is arranged in the filament circuit


of each amplifier. These resistances correspond to the resistances 154 or155, of Fig. 24. However, the corresponding resistance 156 is eliminated inthis system. The system of Fig. 25 affords more delicate graduations than thatof Fig. 24.

The timbre is regulated in the above cases by varying the characteristics ofthe tubes by suitably adjusting the resistances.

Fig. 26 illustrates a system of connections for varying the timbre byvarying the magnetic induction of the transformer core connected in the platecircuit of one of the amplifiers. The primary winding 171 of a transformer 172is connected in the plate circuit of an amplifier. A secondary winding 173 isconnected to the reproducer 174. The transformer is furthermore provided with athird winding 175, the energization of which is varied by the rheostat 176. Byadjusting the rheostat 176, the magnetization of the core 172 is changed, whichcauses a variation of timbre in the reproducer 174. This system is simpler thanthat according to Fig. 25, but does not give such gradual adjustment.

Fig. 27 is a diagram of a complete instrument for two tones. The systemcomprises two “sound generating” control elements 177 and 184, for the firstand second tones respectively, and a “sound volume” control element 2O7.

The “sound generating” control element 177 for the first tone is connectedwith the circuit 179 of an oscillator 178 and the circuit is grounded. Adetector 180 is included in the first system and a detector 187 is included inthe second system. Said detectors are connected by a coupling coil 181 and acondenser 182. A non-inductive resistance 188 is inserted between the grid andthe filament of the detector 180 for the purpose of maintaining the grid ofsaid detectors substantially at the initial potential.

The “sound generating” control element 184 of the second system is similarlyconnected with an oscillator 185 and a circuit 186, the condenser 189, and theresistance 190.

The two detectors 180 and 187 transmit the low-frequency oscillations to theamplifier 193 by means of the transformers 191 and 192. The fixed oscillator194 is connected to the calibrated oscillating system 195 in a correspondingmanner and is also connected with the two tone systems or their first amplifier193. The latter may then control the amplifier systems 197, 198, 199, 200 bymeans of the transformer 196 for the purpose of producing a better effect.These amplifiers are controlled by the rheostats 201, 202 and 203 in the platecircuit and by rheostats 204, 205, 206 in the filament circuit.

The “sound volume” control element 207 controls through the absorptionsystem 208, the oscillating system 209 of the amplifier 210 for the soundvolume regulation. The oscillating circuit 209 feeds the filament of the tube197 by means of the high-frequency transformer 211. The amplifiers 197, 198,199 and 200 then supply the reproducers 213 and 214 through the transformer212, the switches 215 and 216 serving for switching the tones on and off, whilecorrection systems 217, 218, 219 are furthermore provided for the reproducers213 and 214.

The resistances 201, 202, 203, 204, 205, and 206 serve for producingdifferent kinds of tones. The rheostat 220 permits a regulation of the filamentcurrent for all tubes. The condenser 221 serves for the regulation of thetimbre in the reproducer 213. while the choke 222 exerts a similar effect uponthe reproducer 214. If it is desired to dispense with the “sound volume”control element 207, the rheostat 223 indicated in dotted lines should beconnected in circuit.

It will be readily understood that the systems of connection illustrated anddescribed are only a few examples of how the invention may be enlarged upon. Asa matter of course, it is possible to vary the individual systems in many waysaccording to developments made in the wireless industry.

By a phase displacement of the individual sound reproducing systems, anapparent wandering of the sound tones in space may be produced. The inventionmay if desired be used in conjunction with a broadcasting transmitter, wherebythe frequency variation caused by the approach of a body towards the controlelement of the oscillating system will directly influence the broadcastingtransmitter so that the electric oscillations corresponding with the soundoscillations are amplified and directly transmitted. In playing, on thisinstrument, the microphone or microphones and the distortions caused therebyare eliminated, so that a clearer reproduction is assured.

I claim:

1. A tone generating system controlled by the hand and comprising anelectrical circuit embodying an oscillation generator, means in said circuitincluding a conductor having a field which when influenced by a hand movingtherein will vary the resonant frequency of said hand according to the movementof said hand only, and a sound reproducer connected with said circuit foremitting tones according to the electrical variations occurring in the circuit.

2. A tone generating system controllable by an object moving relativethereto, comprising an electrical circuit embodying an oscillation generator,operating means associated with said circuit, including a conductor having afield which when influenced by send object moving therein will vary the


resonant frequency of said circuit, said object having a differentdielectric constant than the medium in which the field occurs, a secondelectrical oscillation generator connected to said circuit and a soundreproducer connected to said generators for emitting tones produced by theinterference of the oscillations of said generators.

3. A tone generating system for producing a plurality of superimposed tonescomprising an electrical oscillating circuit and a control electrode for eachtone, the field of said electrode being controllable by the hand alone whenmoving therein, means including the control electrodes for varying the resonantfrequencies of said circuits in accordance with the tones desired and areproducer associated with all of said circuits.

4. A tone generating instrument played by hand comprising a circuitembodying an oscillation generator, means in said circuit including a conductorexternal thereto electrically influenced by the movement of the hand forvarying the resonant frequency of said circuit at will, a second oscillationgenerator connected to said circuit to produce a beat frequency, a detectorsystem coupled with said circuits, a sound reproducer controlled by saiddetector system and a transformer connected intermediate said reproducer andsaid detector system.

5.A sound or musical tone generating instrument comprising a circuitembodying an oscillation generator, a second oscillation generator producing abeat frequency therewith and means in said circuit including a conductorelectrically influenced by body capacitance for varying the resonant frequencyof said circuit to produce musical tones at will.

6. A musical instrument comprising a circuit embodying an oscillationgenerator, means including an electrode in said circuit for varying theresonant frequency of said circuit at will to produce the desired musicaltones, a second oscillation generator connected to said circuit to produce abeat frequency, an amplifier in said circuit, a detector system connected tosaid amplifier and said second oscillation generator and a sound reproducerconnected to be controlled by said detector system.

7. A musical instrument comprising a circuit embodying an oscillationgenerator, means including an electrode in said circuit for varying theresonant frequency of said circuit at will to produce the desired musicaltones, a second oscillation generator connected to said circuit to produce abeat frequency, an amplifier connected to said second oscillation generator, adetector system connected to said amplifier and the first-mentioned oscillationgenerator and a sound reproducer controlled by said detector system.

8. A sound or musical tone generating instrument comprising an electricaloscillating circuit, means including an electrode electrically influenced bymovement of the hand for varying the resonant frequency of said oscillatingcircuit at will to produce the desired musical tones, an electro-ionic tubehaving a plate and a grid connected to said oscillating circuit to cause anoscillating current to flow therein, said electrode being directly connected tosaid plate and a sound reproducer in said circuit for emitting tones inaccordance with the variations in the oscillations.

9. A musical tone generating instrument comprising an electrical oscillatingcircuit, means including an electrode electrically influence by movement of thehand for varying the resonant frequency of said oscillating circuit at will toproduce the desired musical tones, an electro-ionic tube having a plate and agrid connected to said oscillating circuit to cause an oscillating current toflow therein, said electrode being directly connected to said grid, and a soundreproducer in said circuit.

10. An instrument for producing musical tones comprising an electricaloscillating circuit, means including an electrode in said circuit forcontrolling said circuit to produce the desired tones in accordance with themovement of the hand, two inductances of different values in said circuit, saidelectrode being connected to the larger inductance, and a sound reproducerconnected with said circuit.

11. A system for generating n musical tones, comprising n+1 circuits, anelectrode in each of a plurality of said circuits arranged to be responsive tomanual control and a sound reproducer controlled by the beat frequencies of thecurrents traversing. said circuits.

12. A musical sound generating instrument comprising oscillating circuitsmeans including a manual control electrode in each circuit for controlling thefrequency of the oscillations therein, a detector system for each circuit, aresultant system to which all said detector systems are connected and a soundreproducer controlled by said resultant system.

13.A sound producing instrument comprising oscillating circuits, meansincluding an electrode in each circuit for controlling the frequency of theoscillations therein at will, oscillating systems to one of which each of saidcircuits is coupled, each oscillating system comprising a coupling coil, saidcoils constituting the primaries of a transformer, a secondary in saidtransformer, a calibrated circuit, a coupling coil in said calibrated circuitconnected to the neutral


points of each primary, a generating system to which the secondary of saidtransformer is connected and a sound reproducer controlled by said generatingsystem.

14. A musical sound producing instrument comprising oscillating circuits,means including an electrode in each circuit for controlling the frequency ofthe oscillation therein at will, a detector connected galvanically to eachcircuit, coils connected in series with each detector, condensers connected inparallel to each coil, said coils constituting the primaries of a transformer,a secondary in said transformer, a variable inductance common to all detectorcircuits, a calibrated system comprising a plate and a grid circuit saidinductance being connected to said plate circuit, a generating system to whichthe secondary of said transformer is connected and a sound reproducercontrolled by said generating system.

15. An instrument for producing musical sound notes comprising oscillatingcircuits, means including an electrode in each circuit for controlling thefrequency of the oscillations therein, at will, a detector connectedgalvanically to each circuit, coils connected in series with each detector,condensers connected in parallel to each coil, said coils constituting theprimaries of a transformer, a secondary in said transformer, a variableinductance common to all detector circuits, a calibrated system comprising aplate and a grid circuit, said inductance being connected to said grid circuit,a generating system to which the secondary of said transformer is connected,and a sound reproducer controlled by said generating system.

16. An apparatus for producing music in imitation of musical instrumentscomprising an electrical oscillating circuit, means in said circuit includingan electrode for controlling the oscillations therein, a sound reproducer insaid circuit controlled by the oscillation controlling means, a cathode tubefor said reproducer and means including a filament in said tube for regulatingthe volume of the sound in said reproducer, said last mentioned means alsoincluding a volume control electrode connected to the filament.

17. An apparatus for producing sound tones comprising an electricaloscillating circuit, means including an electrode for controlling the resonantfrequency of the oscillating circuit, a sound reproducer connected with saidcircuit and means including a separate electrode for regulating the volume ofthe sound in said reproducer by varying the electrical field of the electrode.

18. An apparatus for producing sound tones comprising an electricaloscillating circuit, means including an electrode for controlling the resonantfrequency of the oscillating circuit, a sound reproducer connected with saidcircuit, a detector provided wit a filamentary cathode, a battery connectedwith the filament circuit of said detector, a shunt circuit, and a switchadapted to close either the filament circuit or said shunt circuit.

19. An apparatus for producing musical tones comprising an electricaloscillating circuit, means including an electrode for controlling the resonantfrequency of the oscillating circuit, a sound reproducer connected with saidcircuit, means including a separate electrode for regulating the volume of thesound in said reproducer, a tube associated with said separate electrode, arelay energized by said tube, a detector and an amplifier comprising a filamentconnected with said detector and controlled by the armature of said relay.

20. An apparatus for producing musical sound comprising an electricaloscillating circuit, means including an electrode for controlling the resonantfrequency of the oscillating circuit. a sound reproducer in said circuit and asecond oscillating circuit, the electric oscillation constants of whichcorrespond to the mechanical oscillation constants of said reproducer.

21. Apparatus generative of musical sound comprising an electricaloscillating circuit, means including an electrode for controlling theoscillations therein, a sound reproducer in said circuit, a plurality ofelectro-ionic tubes of different characteristics connected in parallel to eachother and in series with said reproducer and separate resistances forregulating the plate and filament current of each tube.

22. Apparatus generative of musical tones comprising an electricaloscillating circuit, means including an electrode for controlling theoscillations therein, a sound reproducer in said circuit, a detector, atransformer, one winding of which is connected in the plate circuit of saiddetector and the magnetization of which transformer is regulated by its otherwinding, a circuit connected with said other winding, a resistance forcontrolling said circuit and a third winding, in said transformer connectedwith said reproducer.

23. The method of obtaining a definite dependence of the change of thefrequency of an oscillating system for producing relative changes in patch ofmusical tones upon the degree of approach of an object toward a controlelectrode characterized by the steps of changing the electrical fielddistribution by varying the relationship of said electrode and said object, andgenerating sound according to the characteristics of said field.

24. The method of producing musical tones in accordance with the movement of


the hand, characterized by Generating electrical oscillations in a circuit,varying the capacitance of a portion of the circuit by movement of the hand inits relation to the circuit, producing from said circuit sounds of variablepitch corresponding to the electrical oscillations and altering the variationsto produce sounds of the desired timbre.

25. In a method of producing musical tones in an electrical continuouslyoscillating system, the steps of generating oscillations in the system andwhich comprises changing the electrical characteristics of said system bymovement of a foreign object in proximitive relation to a part thereof to varythe electrical capacity of a portion of the system.

26. The method of producing physical tones in an electrical oscillatingsystem embodying two oscillation generators arranged to generate an audiblebeat frequency characterized by moving the hand in relation to said system in amanner to change the electrical characteristics of one of said generators only.

27. The method of producing musical tones which comprises generatingelectrical oscillations of ultra-audible frequency, generating otheroscillations of slightly different frequency, varying, the frequency of oneseries of oscillations by altering the electrical characteristics of thegenerating system by moving a body in relation to said system and combiningsaid oscillations to obtain a variable beat-note of audible pitch.

28. The method of producing musical tones of controllable pitch, durationand intensity which comprises varying the constants of the circuit of anelectrical oscillator by moving the hand in relation to an element of saidcircuit, producing from said circuit sound vibrations of variable pitchcorresponding to the electrical oscillations and controlling the soundvibrations to vary the duration and intensity of the tones.

29. A musical instrument comprising an oscillating system embodying means tobe influenced in respect to the frequency of its oscillation by externalconditions structurally unrelated thereto, a sound reproducer controlled bysaid oscillating system and means for controlling the volume of the sound insaid reproducer.

30. Apparatus generative of musical tones comprising an electricaloscillating system embodying means including an outwardly projecting conductorsubject to influence in respect of the frequency of its oscillation by externalconditions neither conductively nor mechanically connected thereto and a soundreproducer controlled by said oscillating system.

31. Apparatus generative of musical tones comprising a plurality ofelectrical oscillating systems to produce a beat-note of audible frequency, oneof said systems embodying an outwardly projecting conductor and subject toinfluence in respect of the frequency of its oscillation by external conditionsneither conductively nor mechanically connected thereto and a sound reproducercontrolled by said systems.

32. Apparatus for generating musical tones comprising two oscillators, eachincluding a resonant circuit and adjusted to produce a beat-note of audiblefrequency one of said oscillators having a portion thereof extending outwardlyto a position for cooperation with the hand of an operator to vary theoscillations without moving the elements of the last mentioned oscillator, anda sound reproducer connected said oscillators.

33. An electrical system generative of musical tones comprisingtone-producing means, said means including electrical circuits, a soundreproducer connected to said tone-producing means and means for varying thevolume and pitch of the tone emitted by said reproducer in accordance with themovements of an operator’s hand in relation to said circuits to generateseparate musical notes of the desired duration.

34. An apparatus of the class described responsive to a moving externalobject comprising an electrical circuit embodying an oscillation generator,means in said circuit including a conductor electrically influenced by themovement of said object for varying the resonant frequency of said circuitaccording to the movement of the object and means connected to said circuit foremitting tones according to the electrical variations occurring in the circuit.

35. An apparatus of the class described comprising an electrical oscillator,a sound reproducer connected to said oscillator, an electrode connected to theoscillator for effecting manual control thereof by variation of the electricalfield around the electrode, means for operating the sound reproducer inaccordance with the variations in the oscillator and means for controlling thevolume of the sound from said reproducer.

36. An apparatus of the class described comprising an electrical oscillator,a sound reproducer connected to said oscillator, an electrode connected to theoscillator for effecting manual control thereof by variation of the electricalfield around the electrode, and means for operating the sound reproducer togenerate musical tones in accordance with the variations in the oscillatorincluding a means for controlling the timbre of said tones.

37. An apparatus of the class described comprising an electrical oscillator,a sound reproducer connected to said oscillator. an electrode connected to theoscillator for effecting


manual control thereof by variation of the electrical field around theelectrode, means for operating the sound reproducer in accordance withvariations in the oscillator, a second electrode for effecting manual controlof the volume of the tones emitted by said reproducer by variation of theelectrical field around said electrode and means including said secondelectrode for controlling the volume of said tones.

38. A tone generating system for producing a plurality of registers ofsuperimposed tones, comprising an electrical oscillating circuit, and a controlelectrode for each register, the field of said electrode being controllable bythe hand alone when moving therein, and means including the control electrodesfor varying the resonant frequencies of said circuits in accordance with thetones desired.

39. An electrical musical instrument comprising means for controlling thevolume of the tones thereof, including an electrode controlled by bodycapacitance.

40. In a method of producing musical tones in accordance with the movementof the hand, the steps of generating electrical oscillations in a circuit andvarying the capacitance of a portion of the circuit by movement of the hand inits relation to the circuit.

In testimony whereof I have signed my name to this specification.

LEO SSERGEJEWITSCH THEREMIN.