US2365567A - Musical instrument - Google Patents

Description

Dec. 19; 1944. LANGER 2,365,567

MUSICAL INSTRUMENT Filed July 4, 1942 2 Sheets-Sheet 1 INVENTOR. W/CHQLHS LEA/GER Dec 19, 1944. N.- LANGER MUSICAL INSTRUMENT Filed July 4, 1942 2 Sheets-Sheet 2 OSCILLHTU? I j r 7w WWW m IN V EN TOR.

HTTOR/VEY Patented Dec. 19, 1944 UNITED STATES PATENT OFFICE MUSICAL INSTRUMENT Nicholas Langer, New ,York, N. Y., asslgnor to Central Commercial Company, Chicago, 111., a

corporation of Illinois This invention relates to electrical musical instruments and more particularly to electric organs employing oscillation generators of the gaseous discharge type as sourcesfromwhich oscillations musical scale are adapted to-berendered'selectively efi'ective upon an electroacoustic translating device in response to actuation of the playing keys of the instrument.

As those skilled in the art know, oscillators em- '10 ploying gaseous discharge tubes, such as glowdischarge tubes, neon tubes, and the like, are generally based on-the property of such tubes that there is a difierence of deflnite and more or less constant character'between the break-down l5 voltage of the tube, at which it becomes conductive, and the extinction voltage of the tube, which is the lowest voltage at which the tube still is conductive after discharge through the tube has been initiated. stantially lower than the break-down voltage, de= pending upon various factors, such as principally the type of gas included within the tube, its pressure, the shape and arrangement of the electrodes,

etc. Tubes of this type may be connected 121325 a plurality of seriallyconnected, two-electrode, cold-cathode, gaseous discharge tubes, said oscilvarious ways with. capacities, resistances and a source of direct current to produce electrical oscillations by alternately charging and discharg ing the capacities in the circuit. The principal advantage of these oscillators is their smail at 30 mentions and inexpensive characwr, particularly when two-electrode gaseous discharge tubes with a cold cathode are employed. Therefore, gaseous discharge tube oscillators could be used at a wa sisal instruments where a very large number of oscillators had to be provided within a restricted space and at a moderate cost.

Cine of the disadvantages of these oscillators w L401 W85 the relatively Small amount sf oscillawry only harmonicaliy related frequencies, high oscillatory potentials derived from each oscillator energy that could be directly obtained, particu larly when the more inexpensive and smaller coldcathode gaseous discharge tubes having only two electrodes, were used. This relatively low output was in part caused by the relatively small amount of. current passed by the coldcathode, two electrode tube in the conductive state, and was also due to the fact that a relatively high resistance of the order of several hundred thousand ohms up to several megohms had to be connected in 0 series with the tube, in order to produce oscillations. Obviously. this reatly reduced the outp t of the oscillations produced.

It is an object of the present invention to provide an electrical musical instrument in which 55 stantiai advantage, for example, in electrical mu-' 3e gaseous discharge tube oscillators are designed and adapted. to produce substantially more use- Iul voltage than heretofore has been possible with tubes of this typ at the tone frequencies of different notes of the 5 I Another-and more specific. object is to provide an oscillationgenerator in which two-electrode gaseous discharge tubes of each individual group ance with predetermined calculations.

I It is a further object to provide a musical in= strument in which each individual oscillation generator employed, itself consists of substantially identical two-electrode, cold cathode glow-discharge tubes connected in series for substantially simultaneous and synchronous [break-down and The extinction voltage is sueaclator being-approximately tuned to harmonically related frequencies and being automatically maintained the exact harmonicaliy related fires quencies by impressing osciliatory energy obtained from'each'osciliator upon at least another one of said oscillators,

Itiis aiso within the contemplation of the in 'vention to provide an electrical musical instru merit in which a large number of oscillation sern erators is employed, each including a plurality oi- 4, serially connected glow-discharge tubes, said oscillators being arranged in groups including being impressed upon at least another one of said oscillators by means of an external, capacitive-1y operative electrode, to maintain their predeter= mined harmonic relationship constant,

Another important object of the invention is to provide in on electrical musical instrument having a plurality at groups of harmonically related oscillators and switching means under the con trol of an operator to draw oscillatory energy from any desired number of oscillators at a time, means for normally maintaining said groups in an inoperative condition, and means operabie by said switching means. to initiate the operation of such groups irom which at least one oscillation is to be withdrawn. l

The invention also contemplates a novel and improved glow-discharge tube oscillator particularly adapted for electrical organs, which is simple in construction, small in dimensions, capable of substantial output of oscillatory energy. and which may be readily manufactured and sold on a practical and commercial scale at a low cost.

Other and further objects and advantages of the invention will become apparent from the following description, taken in conjunction with the accompanying drawings, in which:

Fig. 1 illustrates the circuit diagram or" an oscillator embodying the principles oi. the present invention which a pair of serially connected gaseous discharge tubes is employed;

Fig. 2 depicts a circuit diagram of a similar oscillator in which three series-connected glowdischarge tubes are incorporated;

Fig. 3 shows an oscillation generator circuit, which is a modification of the circuit illustrated in Fig. 1;

Fig. e is a diagrammatic circuit of an oscillator group including live harmonically related oscillators, each oscillator employing a pair of serially connected tubes provided with external electrodes for the purpose of stabilizing the harmonic relationship of the several oscillators; and

5 is the circuit diagram of a portion of electrical organ employing groups of harnionicaily related frequency stabilized oscillators, means being provided for selectively withdrawing oscillatory energy from the several oscillators and disabling all of the oscillators when no oscillations are required.

Broadly stated, in accordance with the Principles of the present invention, I provide a plurality of gaseous discharge tubes connected with each other in such a manner as to have their respective discharge paths in series with each other. The resulting discharge path is connected with capacities and resistances so that the capacitor is alternately charged and discharged at a predetermined rate. Thus, for example, a condenser may be connected across the common, or resultant gaseous discharge path, and a high resistance may be connected in series with such discharge path.-

When now a source of direct current having a voltage higher than the sum of break-down voltages of the individual discharge paths is connected across the resulting structure, the condenser across the conmion discharge path will be gradually charged from the source of direct current through the resistance until its charge potential reaches the break-down voltage ofthe combined discharge paths. At that time the combined discharge paths become conductive and discharge the condenser until the voltage across the condenser will drop below the extinction voltage of the combined discharge paths. Thereafter charging of the condenser will be resumed and the described cycle will be repeated at a rate determined by the capacity of the condenser, the value of the resistance, the voltage oi the source of direct current and the constants of the discharge paths, particularly their break-down and extinction voltages. I have found that although there may be a very substantial difference between the critical voltages of the individual serially connected gaseous discharge paths, current will start and stop flowing through them in such close sequence that for most practical purposes it may be assumed to be simultaneous. This surprising fact may be to some extent explained by consldering that when, for example, two individual discharge paths are connected in series and a source or direct current potential is connected across the same, the potentialof the source will be divided between the two, initially non-conductive discharge paths in a more or less uniform manner, particularly when the tubes are of the same general type and have similar electrode arrangement, gas filling, etc. As soon, however, as one of the discharge paths has become conductive, its resistance will suddenly drop from a very high value to a very low value, generally speaking from several hundred megohms to ill-50,000 ohms, or less. This will concentrate practically all of the potential drop between the electrodes of the remaining non-conductive tube which will break down practically instantaneously. In other words, the break-down of the serially connected discharge paths will occur in such rapid sequence as to be practically simultaneous. The same conditions of operation apply to circuits in which more than two serially connected discharge paths are employed.

A similar oscillatory circuit includes a plurality of serially connected gaseous discharge paths which are connected in series with a high resistance and with a source of direct current having suitable potential, a condenser being connected across the resistance. In this case the gaseous discharge paths will break down practically instantaneously and will charge up the condenser. After the condenser is charged, its potential will oppose that or the source of direct current and the discharge paths will be extinguished. At the same time, however, the condenser begins to be slowly discharged through the shunting resistance. When the potential of the charge of the condenser becomes sufllciently low, the voltage of the source of direct current becomes again effective and the charging cycle begins anew. Oscillations will be produced in the circuit, the frequency of which will be determined by the same factors as in the circuit referred to in the foregoing.

In addition to these representative circuits, various other circuits are possible for the production of electrical oscillations. As a matter of fact, it could be generally stated that in any circuit embodying gaseous discharge tubes, 8. plurality of serially connected tubes of the same type may be substituted for each tube, provided that the voltage of the source of direct current is correspondingly increased. The advantages of the present invention may thus be readily obtained, these advantages residing particularly in the possibility of obtaining a greatly increased oscillatory current and potential output with standard parts and with readily obtainable standard gaseous discharge tubes of low cost and small dimensions. These and other important advantages following from the application of the principles of the present invention will more fully appear from the following detailed description of certain representative circuits into which the invention may be incorporated.

Referring now more particularly to Fig. l of the drawings, a preferred embodiment of the invention will be described. Two glow-discharge tubes Gl and G4 ar connected in series with each other and with a resistance R-l. A source of direct current B-l is connected across the ce- 1 rially connected tubes and resistance to apply a constant potential thereto. A condenser C-l is connected across the two tubes G-l and (3-2. It will be found that oscillations 0! determined freassess? quency will be produced in a circuit oi the described type, provided that the voltage of 8-! exceeds the sum of the break-down voltages or 6-! and 6-2.

Upon completion of the circuit, condenser C-l will be gradually charged through resistance R4. The tubes G4 and G4 bein originally nonconductive, they do not have any appreciable effect on the rapidity of charging the condenser, thi being solely determined by the capacity of C-l, the resistance of R4 and the voltage of B-l.

As soon as condenser has been charged up to a potential corresponding I to the combined break-down voltages of G-l and G4, the tubes will become conductive substantially simultaneously, (as it has been explained in the foregoing) and the condenser will start to discharge through the serially connected gaseous discharge paths or G-l and G-2. This discharge will continue until such time as the potential of the condenser charge decreases below the extinction voltage of. the two tubes, this being the lowest voltage at which the discharge can be still maintained, once it has been initiated. At this time tubes G-I- and 6-2 become non-conductive and charging of condenser C-l is resumed. This cycle comprising alternate charging and discharging of the condenseris continuously maintained until direct current potential is applied to the system in which oscillations of substantially constant frequency will be produced. The frequency of the oscillations is (16- termined by the capacity and resistance and also by the voltage of the source'of direct current. Oi. course, the critical voltages of tubes G-l and G4 (the break-down and. extinction voltages) have also a definite effect on the frequency. Generally speaking, the frequency of the oscillations produced decreases with increasin resistance and capacity and increases with increasing operating voltage, and vice versa. For example, audiofrcquency oscillations may be, produced with resistances from i cnegohm to 20 megohms, capacities or 0.00% to cor microfaracis and voltages of we to 300 volts. These ranges, however, are by no means critical and. wide variations are possi ble. Obviously, the same frequency may be obtained by an infinite number of combinations of values of iii-l, (3-4 and. of the voltage of 3-5, a higher capacity may be compensated for by a lower resistance, or higher voltage, and vice versa.

The oscillatory output may be taken of! in a number of different ways. For example, the primary winding of output transformer may he connected in series with any portion of the cir cult and the output may" be taken on? through the secondary winding of the transformer. an. alternative, a bleedcr resistance be conthe positive terminal of the source or current. As soon, however, as both tubes G-l and 0-! become conductive, their internal resistance will decrease from a large number oi-megohms to a few thousand ohms. In other words. the Potential of point A-l will be shifted considerably closer to that of the negative terminal of source 01' current B-I. The voltage fluctuation at A-l with respect to a point of constant potential in the circuit may reach very high values, well over 100 volts and more. A substantially lower oscillatory potential is obtainable at the Junction point of the two tubes G-l and G4, denoted by reference character A-2.

Fig. 2 depicts an oscillatory circuit which is in all respects similar to that shown in Fig. 1, with the only diflerence that three glow-discharge tubes are connected in series. Of course, the volt age of source of current B-2 has to be generally higher than the sum of the break-down voltages of the three tubes.

' The circuit 01' Fig. 2 includes three two-electrode, cold-cathode, gaseous discharge tubes, such as glow-discharge tubes G4, G4, and (3-4. These tubes are connected in series with each other and with a resistance R-2, tubes and resistance being collectively connected across the nccted in any branch of the circuit and the oscillatory voltage drop along this resistance may be utilized. Particularly when the load has a very high impedance, such as the grid circuit of a thermionic tube, or the external electrode of a gian -discharge tube, a direct connection of such grid or electrode, etc, is possible to a point of the circuit where the potential with respect to a point of fixed potential of the circuit is greatly varying at the oscillatory rate determined by the frequency of the oscillations produced. Such a point is, for example, the junction point of the serially connected tubes 6-5 and G-Z, and resistance R-i, denoted by reference character A-l It will be noted that when tubes (Ii-l and 6-2 are non-conductlve, practically all of the potential drop will be across the tubes so that the potential at A-l will closely approximate that of positive and negative terminals of source of direct current 8-2. A condenser (3-2 is connected across the serially connected tubes M, G4, and 0-5. For'all practical purposes the serially connected discharge paths of the three tubes will function as a single gaseous discharge path having considerably higher break-down and extinction voltages, although it may be pointed out that conduction of current through the various tubes is not exactly simultaneous at all times. The op eration of the circuit of Fig. 2 is exactly the same as that of Fig. l and will be readily understood by those skilled in the art without any detailed explanation. It will be sufllcient to state that electrical oscillations of determined frequency will be maintained in the circuit and may be withdrawn in any suitable manner by means. of capacitive, inductive, or galvanic coupling means. Reference character A-il denotes thejunction point of resistance iii-2 and serially connected tubes 6-3, (3-4 and 6-5, from. where oscillatory potential of the highest value may be obtained. Junction points A-t and 23-5 of tubes and G4, 6-5, respectively, can (provide oscillatory potentials or lower values, that or A- i being higher in value than that of i-ii, for obvious reasons.

It will be readily appreciated more than three gaseous discharge tubes may coimectecl with equal or similar results, and thereby oscilla tions of correspondingly increased amplitude may be produced. Of course, when increasing the number of serially connected tubes, the voltage or the source of direct current has to be likewise in creased.

The oscillation producing ci cuit shown in Fig. 3 is likewise closely similar to that shown in i. In this case the difierence consists in connecting the condenser across the resistance in the circint, rather than across the tube. This will produce a somewhat different waveform, as it will appear from the following description of the circuit and operation of this oscillator.

The circuit of Fig. 3 comprises a pair of glowdischarge tubes (3-6 and G-l connected in series with a resistance R-3 and with a source of direct current 8-3 of appropriate voltage. A condenser 0-3 is connected across resistance lit-3. Provided that the voltage of the direct current source is higher than the sum 01' the break-down voltages of (3-8 and G4, upon completion of the circuit the two tubes will break down at once and condenser C-3 will be charged up. As soon, however, as condenser C-3 is charged, its electro-motive force will be opposed to that of B-3 so that the discharge through the tubes will be interrupted. At the same time condenser (3-3 will begin to discharge through resistance Rl-3. After a certain time the voltage of the condenser charge will decrease suf ciently to cause break-down of tubes G t and G? under the effect of the voltage of "5-3 and a new cycle of charging and discharging of the condenser will begin. The frequency of the oscillations produced in the circuit is determined by the same factors as in the case of circuits i or 2.

It is worth noting that while in the circuits of l and 2 the condenser is charged gradually through the resistance and is discharged practically instantaneously through the tubes, in

the circuit of Fig. 3, the condenser is charged practically instantaneously through the tubes and is discharged gradually through the resistance.

In other words the waveforms obtained by circuits Fig. 1 and Fig. 2 on the one hand, and by circuit of Fig. 3 on the other hand show a more or less reversed configuration, the frequency obtainable by both types of circuits being substantially the same, provided the physical constants of the respective circuits are the same. In view I" the fact that the wave-form of the oscillations enerated has great influence on the tone colors ultimately produced, selective and judicious apication of these two basic types of oscillators has it possible to obtain a wide range of musiry valuable tone qualities. The oscillatory outof the circuit of Fig. 3 may be withdrawn in ircuits of Figs. 1 r 2. For example, a high scillatory potential may be taken off at the point and a somewhat lower oscillatory potential nay be taken off at A-i.

In a plurality of harmonically related oscillators of the type illustrated in Fig. 3 are shown, means being provided for impressing oscillatory potential derived from each oscillator upon the following one, thereby to maintain the barmonic relationship between the various oscillators constant. In Fig. five oscillators O-l, O-2, (3-3, 04 and 0-5, tuned in octaves, are illustrated although, of course, any desired number of oscillators may be employed. Oscillator 04 comprises a pair of glow-discharge tubes G4 and (3-9 connected in series with a resistance R4, a condenser C-A being connected in series with a resistance R4, a condenser C-l being connected across the resistance. Oscillators O4, O4, O-l and O-5 comprise pairs of tubes G-HI and G-l l; (3-H and 6-13; G-ll and G45; and G46 and (3-H, respectively, connected in series with resistances R-5, R-S, R4, and R-8, condensers C-5, C4, (7-1 and C-8 being respectively connected across the corresponding resistances. All oscillators are connected to a common source of direct current B-4 whereby electrical oscillations will be set up in each oscillator. The electrical constants of the various oscillators are so determined that they will produce oscillations the frequency of which is approximately in octave relation. In other words, the frequency of the oscillations produced by oscillators O-I t O-5 are approximately in the proportion of I6], 8!, 4f, 2], and f. To facilitate approximate tuning of the several oscilny of the ways described in connection with thelators to such respective frequencies, condensers C4 to C4 may be 01 the variable type.

Tubes (3-: to G-l'l are each provided with an external electrode E-l t E-lb, respectively. The object of these external electrodes on the tubes is to influence, or to trigger the starting and stopping of a discharge through the respective tubes by means of a potential impressed upon such electrode. Although somewhat loosely, it could be stated that the external electrode has to some extent a similar effect upon the current flow through the tube as the grid of a thermionic tube upon the plate current.

The external electrodes of tubes in the same oscillator are connected in pairs. Thus, external electrodes E-3 and E4 of oscillator 04 are connected to the junction point of serially connected tubes G-i, (3-9 and resistance R4 or oscillator Ol, denoted by reference character A-8. Likewise, external electrodes E-S and 3-6 on the tubes of oscillator 04 are connected to the corresponding Junction point A-B in oscillator 04, external electrodes E4 and 3-8 of oscillator 04 are connected to the corresponding junction point A-ill of oscillator 03, and external electrodes E4 and E-Hi of oscillator O-i are connected to the corresponding junction point A-H of oscillator 04. In view of the fact that at points A-8, A-9, A-ili and A-i strongly varying oscillatory potentials are present, such potentials will be impressed upon the tubes of subsequent oscillators and thereby will stabilize the frequency relationship thereof. Asoscillators Oi to (1-5 are approximately tuned in octave relation, the triggering voltages on the external electrodes of the tubes will time the break-down and extinction or the discharge through the various tubes in such sequence that the octave relation will be permanently and accurately maintained even though some or all of the physical constants of the several oscillators may vary to a substantial extent. Experiments have shown that after a group of cascaded oscillators or the type shown in Fig. 4 has been locked in the desired harmonic relation, even intentional attempts to tune one of the oscillators away from the original frequency, for example, by changing the capacity of C, the resistance of R or the voltage of B are of practically no effect upon the oscillators which thus may be maintained at the proper relative pitch indefinitely. It has been found that the voltage of 13-4 could be changed by as much as or volts, without disturbing the relative pitch of the oscillators, although, of course, the absolute pitch would change with the voltage. In order to maintain also the absolute pitch likewise constant, which is of great importance in electrical organs and similar electrical musical instruments, it is in some cases desirable to impress a stabilizing oscillatory potential of constant frequency upon oscillator O-l by means of external electrodes E-l and Fri. This external stabilizing voltage may be taken from any oscillation producer having a high stability, such as a thermionic tube oscillator of suitable construction, a tuning fork oscillator, etc., and its frequency may be identical with that of the desired frequency of oscillator 04, or at least is harmonically related thereto. In this manner, both the absolute pitch and the relative pitch of the oscillators will be positively maintained.

In my. U. on August 12, 1941, I have disclosed systems of harmonically related glow-discharge tube oscilla- 76 tors in which the desired accurate frequency re- 8. Patent No. 2,252,189, issued to me 2,305,507 lationship is maintained by impressing a signal.

disclosed herein resides in the series arrangement of a plurality of glow-discharge tubes or similar gaseous discharge devices whereby a much higher oscillatory potential may be obtained. Due to the fact that the stabilizing circuit shown in Fig. 4 provides oscillatory stabilizing voltages several times as high as obtainable by the circuits disclosed in the said patent, the stabilizing effect is substantially improved so that even under rather unfavorable operating conditions excellent and practically permanent stability of the oscillations produced is obtained.

those skilled in the art will readily understand, in an electrical musical instrument, or orcan, a very large number of oscillators of the type disclosed herein is necessary. Thus, for example, in an organ having a range of 7 octaves and uned in the tempered scale from C to C, 35 oscilors are necessary. Preferably, these as oscilcrs are subdivided in twelve groups, each. group nicluding seven. oscillators tuned in octave relation to the same note of the tempered scale, with the exception of the 3 note group, which includes A octaves. Each group has the octavely related oscillators arranged in substantially the same coordination as shown-in Fig. 4.

cascaded oscillatorscrranged in a plurality oi note groups, generally velve, corresponding the number of notes in a single octave oi the tempered scale, 0, co ii, dil e, f. f v, was heretofore unavoidable to have all of so o cillators of all of the note groups producing tlons all of the time and to provide suitable lg or switching means whereby oscillatory y is withdrawn from certain of the oscilla in accordance with the musical composition to be interpreted. This conventional ctice introduced crave problems in the way of ding avoid cross-talk, cross modulation similar parasitic oscillator phenomena which ed a background noise orinterierred with rcper tone color or the purity of the musical is ultimately produced. This will be readily cciatecl ii it considered that in an eleccan organ of practical construction as many as 1 I, even more, oscillators have to be mainecl continuous oscillations. In view of the "hat the power supply of all oscillators is orally common in order to simplify wiring to reoluce cost, there is usually some remaincoupline: between the several oscillators. in on, even with careful shielding, leads carry Terent frequency oscillations have to be oed in close proximity and some pickup of story energy clifiicult to avoid unless each or at least each note group is very efully decoupled and also shielded. The proholeouate shielding is further aggravated board and. associated contacts in which as contact blades are necessarily arranged close pi to each other and where convolitional ethods of shielding are executed only tli llficulty. As a result, prior electrical odying cascaded oscillators generally tiered from a certain amount of background which was almost impossible to avoid unless extremely complete shielding was practiced at great inconvenience and expense.

I have discovered that this problem of crosstalk in electrical organs may be solved in a re markably simple and inexpensive manner by departing from the conventional practice of having the groups of cascaded oscillators oscillating all of the time. Instead 0! this old and unsatisfactory practice, I prefer to have all groups or casceded oscillators normally inoperative and to start the complete group oscillating only when any one of the notes in the particular group is required. in other words, only those groups are operating and producing oscillations at any time, from which at least one note is needed at that particular moment. Thus, for example, when the player desires to produce a C major chord including the notes C, E, and G, depression of the corresponding keys of the keyboards will first start the corresponding note group oscillators operating and immediately after will withdraw oscillatory energy from the particular oscillators of such groups corresponding to the depressed keys. In this manner, when the above mentioned chord is played, the rest of the note group oscillators will be inoperative and consequently no non-harmonic parasitic oscillations may he picked up, even in the complete absence of any shielding. Eiiven though some very slight amount of oscillatory energy maybe picked up from. some or" the oscillators oi the same name as the notes played, these will be harmonically related the played notes and will not influence the desired musical effect, except perhaps for a slightem harming oi some oi the harmonics of the said notes.

This simple, but at the same time extremely valuable novel. principle in the design and con struction oi electrical organs will be better understood referring to the circuit of Fig. 5 in which the wiring of a single note group with a keyboard and associated contacts is illustrated, embodying the principle broadly stated in the foregoing.

Referring now to Fig. 5 of the drawings, the note group embodying the principles of the pres= ent invention comprises five ootavely related glow discharge oscillators 6-8, 0-3, G t, and (3-H. These oscillators each include a pal: of glow-discharge tubes GAB, G-QS; G-til, 6 -28; (G -22, (I -23; ill-2d, 6-35; and (3-25, (3-2, re spectively, connected with a. condenser oi ad- ;lustalole capacity G 9, C-ll), C-l i, (53-82 and C-it, respectively, and a bleeder resistance R-M, Elf-l5, le -iii, and RI- id, respectively. The bieeder resistances are of a relatively low value, a few thousands ohms, and their object is to obtain a potential drop which may constitute the signal to be selectively introduced into the output systern by means oi key-controlled switches, as it will presently appear. Dscillators 045 to G-lu are all connected across the positive and negative terminals oi a source of direct current the voltage which may be adjusted Within a narrow range by means of a potentiometer P connected across a portion thereof.

High resistances of the order of several megohms, lat-ill, it-l E, R4? and R-lt have one of their ends respectively connected to the point of junction of the serially connected tubes and of the variable condensers of the oscillators 9-8 to 0-20, while the other end of allof these resistors is connected to a common bus bar l). lhis bus bar is normally disconnected from the ncgative terminal of source of direct current B-S so that all or the oscillators are inoperative. Switches 8-8, 8-3, 8-5, 8-1, and 8-3, respectively operable by depression of keys K4, K4, K4, K-l, and K-! are connected between common leads F and H of which 1' is connected to bus bar D and H is connected to the negative terminal of 134. Thus, depression of any one of the playing keys K-l to 8-! will cause closing of one of contacts S-l, 84, 8-8, 8-1, 8-! and thereby will connect bus bar D to the negative terminal of 3-5; This will complete the circuit of oscillators -8 to O-lfl, all of which will produce oscillations of determined musical frequencies.

Tubes 6-18 to G-Zl are each provided with an external electrode E-ii to E40, respectively, connected in pairs coordinated to tubes of the same oscillator. These pairs oi external electrodes are electrically connected to points of varying oscillatory potential in the-preceding oscillators. external electrodes 3 and E-i I are connected to the junction point of connected tubes Cir-l0, (3-H and condenser 6-9; electrodes E-lB and E-li are connected to the junction point of tubes (3-20, (3-2! and condenser C-IO; electrodes E-l'l and 12- are connected to the junction point of tubes (3-22, 6-23 and condenser 0-H; and electrodes E-IS and ill-20 are connected to the junction point of tubes (3-2 2, (3-25 and condenser 0-12. Oscillators 0-0 to 0-10 are approximately tuned in octave relation but the eifect of external electrodes Si-i3 to E40 will be to lock them-in accurate octave relation to have relative frequencies of 16;, 8;, 47', if, and 1, respectively. Adjustment or potentiometer P connected across a portion of 13-! makes it possible to change the operating voltage of all oscillators at the same time so that their pitch may be simultaneously raised or dropped without, of course, alfecting their relative pitch or intervals, which will remain that of an octave throughout. In some cases it may be desirable to impress an external stabilizing voltage derived from a stable oscillator, such as thermionic tube oscillator, tuning fork oscillator, etc., and preferably having the frequency of I81 upon external electrodes E-ll and E-l2.

Each of the keys K-l to K-S is provided with a second contact or switch, 3-2, 8-4, 8-8, 8-8, and 8-10, respectively. These contacts have the object of controlling the withdrawal of oscillatory energy from the various oscillators in accordance with the wishes of the operator.

The oscillatory energy or signal is withdrawn through decoupling resistors R-IS to R43 of the order of 10,000 to 50,000 ohms. One end of these resistors is connected to the upper end of bleeder resistances R- to R-IG, respectively, while their other end is connected to the upper contact spring of switches 8-2, 8-4, 3-6, 5-8, and 8-H], respectively. The lower contact of said switches is connected to a common bus bar I, and thereby to one terminal of the primary winding of an output transformer T, the other terminal or which is connected to the negative terminal of source of direct current 8-.

From the foregoing description, the operation of the stabilized group of harmonically related oscillators will be readily understood by those skilled in the art. In the normal condition of rest, that is when none of the keys is depressed,

oscillators 0-8 to 0-" are inoperative. There being no oscillations produced, the problems of shielding and of parasitic QsciIlatiQns cross-taIk, etc., are non-existent. Upon depression of any one of keys K-l to K-l, bus bar D is connected to the negative terminal of'B-i by the upp r one assure? of the key switches and all of the oscillators o! the group start oscillating. A fraction of a second after, the second or lower switch of the same key is likewise closed whereby oscillatory output corresponding to the depressed key is introduced into the primary winding of output transformer T. The secondary winding of this transformer may be electrically associated with an amplifier and a sound producing means (not shown) whereby the oscillations withdrawn are amplified and converted into sound. In case more than one key is actuated at the same time, output of the other oscillator will be likewise withdrawn and impressed upon the same transformer with similar results. In view of the interposition 0! decoupling resistances 12-! 8 to 12-23, which are relatively high in value in comparison to resistances R-H to lit-I8, the reflection of energy from one oscillator to the others, robbing of one oscillator by another and the like undesirable phenomena are avoided at the time when more than one key is operated simultaneously.

Obviously, in a complete electrical organ a number of note groups are employed, preferably twelve, corresponding in number to the number of notes within an octave of the tempered scale. Each of the groups of octavely related oscillators includes a plurality of octavely related oscillators, such as 6 or 7, in accordance with the desired range or gamut of the organ. or course, certain of the elements of the note groups may be in common for all groups, such as the output transformer, the amplifier and speaker and the source of direct currentwhereby the circuit may be considerably simplified It will be noted that the principles of the present invention provide a number of important advantages. First of all, a novel and improved oscillator is provided employing gaseous discharge tubes and capable of a substantial output of oscillatory energy.

It is to be also observed that the oscillators embodying the present invention make it possible to obtain substantial outputs of oscillatory energy varying at an audio frequency rate .by employing gaseous discharge tubes, particularly glowdischarge tubes of conventional design and of small dimensions.

Moreover, oscillatory potentials of very high value may be readily obtained whereby harmonically related groups of oscillators may be maintained in their accurate frequency relation indefinitely without requiring any complex circuits. The present invention also teaches the provision of an electrical organ of extremely simple and inexpensive construction which may be provided at a fraction of the space and cost requirements of prior electrical musical instruments and at the same time is free from the problems of crosstalk, parasitic oscillations, and the like which made the construction of prior electrical organs involved and expensive.

Although the present invention has been disclosed in connection with a few preferred embodiments thereof, variations and modifications may be resorted to by those skilled in the art without departing from the principles of the present invention. Thus, while I prefer to employ glow-discharge tubes of the type in which two cold electrodes are arranged in a sealed vessel containing neon gas under reduced pressure. two-electrode tubes containing other gases, such as argon, etc., may be employed with equal or similar results. Likewise, it is possible to employ two-electrode tubes in which the cathode is sponsive to actuation of said playingkey for rendering said generator effective upon an amplifier.

10. In an electrical musical instrument employing a playing-key, means for producing separate waveforms of oscillatory potential having substantially similar frequency and voltage characteristics and for utilizing said separate waveforms to provide a single waveform having the same frequency as any one of said separate waveforms and a voltage which is equal to the sum of ali of said separate waveforms, said means, com prising a plurality of glow-discharge tubes, each which having but two electrodes, the electrodes of said tubes connected in series and providing a subdivided gaseous discharge path for substantially synchronous periods of conduction and nonconcluction through subdivisions of said path and calf. tubes operating to produce said separate waveforms, a source of direct current for operating said tubes and having a voltage in excess of the sum of the break-clown voltages of said tubes, a resistance in series with said discharge path and said source and providing a closed circuit sh rewith, a condenser in said circuit and alteratelf, charged and discharged during consecuperiods conduction and non-conduction through said discharge path, and means responsive to actuation of said playing-key for rendering combined output voltages of said tubes offective upon an amplifier as a single waveform of I *"ial of predetermined tone frequency.

1 In an electrical musical instrument emioying a playingdrey, means for producing for playing-key waveforms of potential having substantially similar frequency and voltage characteristics and for simultaneously utilizing said separate waveforms to provide a single waveform having the same frequency as any one of said separate waveforms of potential and a voltage which is equal to the sum of all of said separate waveforms, said means comprising a pair of serially connected glow-discharge tubes in which each thereof has but two-electrodes, a source of direct current, and a resistance, all in series and forming a closed circuit; and a condenser connected into alternate charging and discharging relation with said last mentioned circuit at a rate substantially determinedby the time constant characteristics of said circuit said tubes being conductive and non-conductive during substantially identical periods of time regardless of differences'in their physical constants; and means responsive to actuation of said playing-key for rendering the combined output potential of said tubes effective upon an amplifier.

12. In a key-responsive, electrical musical instrument employing an output circuit; means for producing alternating potential of predetermined voltage and tone frequency, said means comprising a plurality of substantially identical, two electrode, gas-discharge tubes connected in series, a source of direct current, and a resistance all in series and providing a circuit; and a condenser connected into alternate charging and discharging relation with said circuit whereby oscillations of a frequency determined by the time constant characteristics of said circuit are produced, said circuit having oscillatory potential of high amplitude at the juncture point of said tubes and resistance and oscillatory potentials of successively lower amplitude at the juncture point of said tubes, and means responsive to actuation of the key of said instrument for rendering said tubes effective to produce in said output circuit said waveform of potential of predetermined fre quency and voltage.

13. In an electrical musical instrument employing an output circuit; a system for simultaneously producing a plurality of electrical oscillatious having constant frequency relationships; said system comprising a plurality of gaseous discharge tube oscillators tuned to harmonically related frequencies; each of said oscillators in cluding a plurality of identical serially connected gaseous discharge tubes having a resistance connected in series therewith and a condenser; means for supplying unidirectional potential to said oscillators to cause substantially synchronous periods of conduction and non-conduction of said tubes and generation by said tubes of corresponding output waveforms of the same frequency and voltage; means for impressing the oscillatory potential derived from an oscillator upon at least another oscillator to maintain the harmonic rela tion thereof constant; and means for rendering the output waveforms simultaneously produced by any selected oscillator effective in said output circuit.

14. In an electrical musical instrument employing an output circuit; means for simultaneously producing for each tone of an assigned vibration frequency a waveform which is the sum of simultaneously generated corresponding waveforms of potential of the same frequency and voltage, said means comprising a plurality of glow-discharge tube oscillators tuned to harmonically related tone frequencies, each individual oscillator including a plurality of serially connected glow-discharge tubes having a resistance connected therewith and a condenser; means for supplying unidirectional potential to said oscillators to cause substantially synchronous periods of conduction and non-conduction of said tubes and simultaneous production of corresponding waveforms of potential of the same frequency and voltage; means for interlocking said oscillators to maintain a given frequency relationship thereof; and means for impressing the output potential from any oscillator on said output circuit.

15. In an electrical musical instrument, a plurality of oscillators of harmonically related tone frequencies each individual oscillator comprising a plurality of substantially identical serially connected glow-discharge tubes, a source of energy for said tubes means for operating the tubes of any selected oscillator to effect synchronous production by said tubes of oscillations having substantially like characteristics, means for utilizing said oscillations to provide a waveform of potential whose voltage is equal to the sum of the voltages of the synchronously produced oscillations, and means for utilizing said waveform as a tone frequency source for actuation as desired of an electroacoustic translating device.

NICHOLAS LANGER.

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