US2429226A - Electrical musical instrument - Google Patents

Description

Oct. 21-, 1947. J 'M. HANERT 2,429,226

' ELECTBICAL MUSICAL INSTRUMENT Filed Sept. 14, 1942 s sheets-sheet 1 llallllltrvlvlllt'tull 5 Sheets-Sheet 2 J M. HANERT Oct. 21, 1947.

ELECTRICAL MUSICAL INSTRUMENT Filed Sept. 14, 1942 Oct. 21, 1947.,

J. (M. HANERT ELEQTRIOA L MUSICAL INSTRUMENT Filed Sept. 14, 1942 s Sheets-Shet a Patented Oct. 21, 1947 ELECTRICAL MUSICAL INSTRUMENT John M. HanerhWilmette, 111., assignor to Hammond Instrument Company, Chicagoylll' acorporation of Delaware Application September 14, 1942', Serial No, 458,305

My invention relates generally to electrical musical instruments and-more particularly to improved duplex melody instruments upon which two notes may be played simultaneously.

The invention is of peculiar utility when used as a substitute for, or as asupplement to, the bass or pedal clavier section of a pipe organ, or any-other type of organ. The pipes for the bass section of a pipe organ are the largest and most expensive in the organ and, as a result, even the largest pipe organs are considerably limitedas to possible tonal variation in their bass sections.

It is therefore an object of the invention to provide an improved means for producing the bass tones of. an organ.

A further object is to provide an improved frequency generating system for electrical musical instruments, utilizing the principle of-frequency division.

A further object is to provide an improved melody type of instrument having a keyboard, an electrical tone frequency generating system, and output system, which is effective to sound the tones corresponding to any two keys Which-may be simultaneously depressed, or to sound the highest and lowest of any three or more'keys which may be simultaneously depressed.

Other objects will appear from the following description, reference being had to the accompanying drawings in which:

Figure 1 is a wiring diagram of the keyboard anda portion of the frequency generating system of the instrument;

Figure 1a is the wiring diagram of the circuits for frequency division, tone quality controlling, and for amplifying the signal and translating it into sound; and

Figures 2, 3 and 4 are schematic wiring diagrams of modified forms of dividing circuits.

The invention may be utilized for the production of tones in any desired frequency range, but has particular utility when used as the bass sec-' tion of an organ, and the invention is therefore described herein as embodiedin such form.

-Referring to Figure 1, the instrument is illustrated as comprising a pedalboard of the usual range of 32 notes" extending from the low note CB (32.703 C. P. S.) to the higher note G2 (196.00 C. P. S.). The keys bear reference characters corresponding to thelpitc'hes of the tones ordinarily produced upon depression thereof.

Each of the'keys C to G2 is provided with an actuator, indicated by a dotted line in the drawmallyto be-in contact with a fixed contact l2, andare adapted when the associated key is depressed to break the contact with the contact I2 and tomake contact with a fixed contact 14. Similarly, the switches II are normally in engagement with contacts I 3. and are adapted, when the key is depressed; to engage fixed contacts l5. It will be noted that the switch arms l0 are in series and that the contact l2 for the key C0 is connectedto-ground, while the switch arm III for the highest key G2 is connected to a conductor [6. The contacts 14 are connected to taps of an inductance'winding L2 wh-ich is in inductive relation with a feedback winding L4.

Inasimilarmanner the switches II are connected in series andnormally engage their contacts 43. The contacts l5 of these switches are connected to taps of a tuning inductance L3 which is in inductive relation with a feedback winding L5;. The endsof theinductances L2 and ba beyond thekey G2. are grounded. The switch I I for the key C0 is connected to a conductor ll.

Theinductances L2 and L3 form parts of oscilla-torswhichinclude respectively triodes 20 and 2t; The. triode. 20 comprises. a cathode 22, a grid 24.;and a1plate26, while the triode 2| includes a cathode 23, a. grid 2 5.and a plateor anode 21. The conductor I6 is connected to the grid 24 through a grid-bias resistor-R2, bypassed by condenser C2,; and is. connected to ground through a tuning condenser C4. Similarly,v the conductor I1 is connected'to the grid: 25 through a grid resistor R3', by-. passedby condenser C3, and is connected to ground through atuning condenser C5.

Plate current is. supplied to the triode 2|! through a. load resistor R4 connected-to the plate 26-.fromi.asuitable source of direct current potential-dndicated by a terminal +300 v. Similarly plate current for the triode 2| is supplied 2 keysiwill; through the closure of its switch [0,

tunev theoscilltrtor'tube 20 to the pitch represented'by such key, while the lowermost of such depressed keys' will tune the oscillator tube 2| tothespitch-represented bysuch key. When three or more keys are simultaneously depressed, depression of the intermediate keys has no effect upon the tuning of the oscillators.

The output signal of the oscillator 20 is transmitted through a blocking condenser C6 to a conductor 28, while the output signal of the oscillator 2| is transmitted through a blocking condenser C! to a conductor 29.

A non-linearly operating pentode 30 has its cathode 32 connected to ground through a biasing resistor R6, and its grid 34 connected to the conductor 28 through a series grid resistor R8, the conductor 28 being connected to ground through a grid resistor RIO. The screen grid 36- of the pentode 30 is connected to a suitable source of direct current potential indicated as a terminal +125 v., while the suppressor grid 38 is connected to the cathode 32. The plate 40 is connected to a suitable source of plate potential indicated as a terminal +300 v, through a load resistor BIZ, and is connected to a conductor 42 through a blocking and charging condenser C8.

The oscillator 20 may have a distorted half wave rectifier type wave shape output, but the pentode 30 is biased so as to convert this wave into a generally rectangularly shaped wave, since the negative portion of the input wave is cut off by virtue of the negative grid bias, while the positive portion of the input wave is cut off due to the change in the input impedance of the grid circuit of the pentode. A pentode of the 6J7G type operates satisfactorily for this purpose.

A pair of diodes 44, 46, which may be of the 61-16 type, are provided to rectify the output of the pentode 30. For this purpose the cathode of diode 44 is connected to the conductor 42 while its plate is connected to ground and the diode 44 will therefore conduct to ground the negative portion of the output wave of the pentode 30. The diode 46, however, has its plate connected to the conductor 42, while its cathode is connected to a terminal 4'! which is connected to the plate 48 of a triode 50. The cathode 52 of the triode 50 is connected to ground while its grid 54 is connected through a current limiting resistor RM and a tertiary winding L6 with a suitable source of biasing potential indicated as a terminal 7 V.

A charge accumulating and blocking condenser CIO has one terminal connected to the terminal 4], while its other terminal is connected to ground through a primary winding L8 of a transformer T2, the winding LB having a plate load resistor RIB connected in parallel therewith. The con-' denser C| has a value large with respect to that of the condenser C8, its value being determined by the number by which division of the output frequency of the pentode 30 is desired. As utilized in the embodiment of the invention disclosed, the condenser Clo will be chosen to have such value that two positive pulses through the diode 46 will be required to charge the condenser Cl 0 to a sufliciently high value that plate current will flow in the triode 50 despite its substantial negative bias. The triode 50 may be of the 6J5G type.

The transformer winding L8 is so phased with respect to the winding L6 that as the plate current commences flowing through the triode 50, the bias on the grid 54 will be less (i. e., its potential will be raised to a less negative value than its normal 7 v. biasing potential), and as a result, as soon as any plate current commences flowing through the triode 50, the rate of flow will increase rapidly until the charge on the condenser C|0 has been reduced to value such that further increase in the potential of the grid does not cause a corresponding increase in plate current. During the time that the plate current flow through the triode 50 is decreasing, the inductance L6 will of course be effective to increase the grid bias at an accelerating rate so that the bias on the triode 50 will rapidly return to a value beyond cut off. As a result, the signal across the winding L8 will be a sharply peaked wave.

A secondary winding L|0 of the transformer T2 is connected to a second non-linear pentode 56 which operates in a manner identical with that of the pentode 30. The elements connected to the pentode 56 are likewise substantially identical with those associated with the pentode 32. The output of the pentode 56 is connected through the blocking and charging condenser C|2 with a conductor 60, and the latter is connected to the cathode and plate respectively of diodes 62, 64, the plate of the tube 62 being grounded and the cathode of tube 64 being connected to a terminal 66, The terminal 66 is connected to the plate of a triode 10 which may be identical with the triode 50 and have similar circuit elements associated therewith. A blocking and charge accumulating condenser C|4 corresponds to the condenser C||| associated with the triode 50. The output of the triode I0 is transmitted to a terminal 12 through the secondary winding L|2 of a coupling and feedback transformer T4. One end of the secondary winding L|2 is grounded, While the other end is connected to the terminal 12 through a decoupling resistor RIB.

As previously pointed out, the signal supplied by the oscillator 20 has its frequency divided by 2 by virtue of the first frequency dividing stage which includes the pentode 30, diodes 44, 46 and triode 50. In a similar way the pentode 56, diodes 62, 64 and triode l0 and their associated circuit elements constitute a second frequency dividing stage, dividing the frequency of the output of the first stage by 2, so that the frequency of the signal across the secondary winding L|2 will be one fourth of that of the oscillator 20.

Means are provided to successively divide the frequency of the output of the oscillator 2| by the factor of 2, the first stage of such frequency divider system including a pentode 3|, diodes 45, 41, triode 5| and associated circuit elements similar to those previously described. The second stage of frequency division includes a pentode 51, diodes 63 and 65 and triode 1|, the first stage being coupled to the second stage through a transformer T3 and the output of the second stage being coupled to the terminal 12 through a transformer T5, the second winding L|3 of which has one terminal connected to ground and th other terminal connected to the terminal 12 through a decoupling resistor RIB.

Since these frequency division stages are essentially identical, the foregoing description of the stage which includes the non-linearly amplifying pentode 3|! will suffice for an understanding of the construction and operation of the other stages, it being noted that the input of the first stage which includes the non-linear amplifying pentode 3| is connected to the conductor 29, thus to receive a signal from'the oscillator 2|.

The terminal 12 is connected to the grid of a linearly amplifying pentode 82, the cathode and suppressor grid of which are connected to ground, the screen grid 84 connected to a terminal v., and the plate 66 connected through a load resistor R20 to a terminal +300 v. A- grid resistor R2I is connected between the grid 80 and a suitable terminal forsupplying the negative grid bias.

Connected 'intparallel with the load resistor R (1. e., between the plate 86 and a terminal +300 v., is a series of filtering meshes 88, 89, 90

I04 connected to the ungrounded terminal of the secondary LIII through a decoupling resistor R24 as well as being connected through a decoupling resistor R with the ungrounded terminal of the secondary winding LII of the transformer T3. The grid I 84 is also connected to a suitable operating bias potential through a grid resistor R21. The output of the amplifying pentode I02 is adapted to be modified by filtering meshes I08, I01, I08 and I09 upon selective opening of one or more control switches I I 0 in a manner similar to that described with the generally corresponding output circuit of the pentode 82. The output of the pentode I02 is impressed upon the conductor 94 through a decoupling resistor R26.

A linearly amplifying pentode II2 has its grid II4 connected to conductors 28 and 29, decoupling resistors R28 and R29 respectively, and is supplied with a suitable operating bias through a grid resistor R3I, The output circuit of the pentode II2 includes a series of filtering-meshes H6, H1, H8 and II9 adapted to be selectively rendered effective by opening one or more of a plurality of switches I22. The output of the pentode H2 is also coupled to the conductor 94 through a decoupling resistor R30. The pentodes I I 2 and I 02, and their associated circuit elements,

are essentially identical and for this reason these parts have not been described in detail.

In using the instrument, it is played in the manner of a conventional organ pedal clavier with the exception, however, that the instrument will be capable of playing only two notes simultaneously; It is only upon extremely rare occasions in organ literature that the score' calls for playing more than two pedal notes simultaneously, and even on such rare occasions the organist seldom follows the score because of the difficulty of execution. Thus, the pedal clavier instrument of this invention is, for all practical purposes, played in a manner exactly the same as any polyphonic organ pedal clavier- As previously pointed out, the depression of any pedal results in connecting a predetermined portion of the inductance L2 into the tuning circuit of the oscillator 20, and in doing so, the switches I0 of all lower keys are disconnected and thus rendered ineifective. Similarly, the depression of such key causes the connection of a predetermined portion of the inductance L3 in the tuning circuit for the oscillator 2|, and disconnects the switches II of keys corresponding to higher pitches from the tuning circuit so that thereafter depression has no effect upon the tuning ofthe oscillator. Thus, the oscillator 20 will be tuned to the highest of any of a plurality of simultaneously depressed pedals, while the oscillator 2| will be tuned to the lowest of any of upon their grids.

such plurality of depressed keysl If only onekey is depressed; bothoscillators will be tuned to" the 2 same frequency. 7

It will be noted that the inductances L2 and L3 are variable for initially tuning the oscillators, such variationbeing preferably effected by adjusting the air gaps in the cores of these coils. This tuningmay be done initially in the course of production of the instrument, and will ordinarily not require readjustment for long periods of time.

Aspreviously pointed out, the signals from the oscillators 20:"and 2|, tuned to the desired fre' quencies by the depression of one or two pedals,

have their amplitude held constant by the am-- plitude limiting tubes 30 and 3| respectively. Thus, the output waves of these tubes are of uniform amplitude irrespective of variations in the frequency or amplitude of the signals impressed Because ofthis function of the tubes 30 and 3I, the dividingsystem is rendered extremely stable.

Thus, the diodes 44, 46 and 45, 41 are supplied with signals of constant amplitude, and

relative to the capacity of the condenser 08 is so chosen that the potential across the condenser CI!) will build up to a value sufficient to cause the plate current to flowthrough the triode50 when either 2, 3, 4 or any reasonably large integral number of impulses have been supplied to the-condenser CIO. Although the operation of the circuits associated with the tubes 30 and 50 has been described as producing a frequency division by using 2 as the divisor, sub-multiples of the input frequency using other integers of 3 and higher as divisors may be employed. This divider circuit may be used to divide the frequency by divisors running upinto the thousands, and its division will be mathematicallyexact, depending upon the stability of the circuit elements. Using circuit elements of mathematically accurate divisions by a factor of 10 may easily be obtained, and division by higher divisors may be obtained within relatively small percentage variations from mathematically exact frequency division.

Assuming, as initially described, that division of the stage including the tubes 30, 50 and 3 I, 5|

is by a factor of 2, the output of these stages will a be an octave lower than the input frequency, and

organ nomenclature, the switches 92 correspond A to the I6 stops of the pedal division, while the switches IIO correspond to the 8' stops 'of the pedal division and the switches I22 correspond to the 4' stops of the pedal division. By operating the switches of these several groups in various combinations, complex pedal tones consisting of octavely related tone qualities may be produced.

While the invention has been described as applied to the production of the tones controlled by a pedalboard, it will be clear to those skilled in the art that by suitable changes in the circuit elements the registerof the instrument-maybe commercial tolerances, I

changed. For example, one of the oscillators 20, 2| together with a series of cascaded stages of frequency division might be utilized as the frequency generating apparatus for instruments of the types shown in Hammond et al. Patent No. 2,233,258 or in my prior Patent No. 2,254,284.

The dividing circuit of the invention is particularly adapted for division of frequency of a variable frequency oscillator or other variable frequency source because it is extremely stable throughout a wide range of the input frequency. Thus, substantial changes in the input frequency do not in any way impair the stability of the dividing stages. The reason for this is that each change that occurs in either voltage or current in the circuit elements which are connected together to form the divider system is initiated solely by the presence of a signal pulse transmitted by condenser C8 to a divider system. For example, the charge on condenser CIO increases by discreet increments, each increment of voltage being a reflection of a change in input conditions on the grid 34 of tube 30, which is supplied by the signal source. Thus, the amplitude at which the tube 50 discharges is a function of the number of times that condenser C8 has charged condenser CIO and is not a function of the absolute frequency generated by the oscillators 20 or 2|.

In this respect this frequency divider differs in operation from relaxing dividers, from multivibrators, blocking oscillators, etc. In these latter types of frequency controlled devices there are change in polarity, voltage, and current in the elements of the oscillator system which change, not because of the presence of a controlling signal, but because of their own time constant functions, e. g., the charging of a relaxation condenser through a charging resistance after said condenser has been discharged by a gaseous discharge tube having a grid which was operated positively by a controlling input signal. In the latter exemplary case the controlling signal operates to cause the discharge of the condenser, but the rate of charging of the condenser is determined by constants of the circuit elements associated with the condenser, and the rate is such that frequency division by some factor would occur for a given input frequency. Thus, this type of frequency divider divides certain frequencies only, whereas the frequency divided of this invention divides all frequencies over an extremely wide audio frequency spectrum. There are no time constant elements in the frequency divider which are in any Way comparable in time to the period of the frequency being divided. All potential changes in the operation of the divider circuit of this invention are signal controlled.

This non-linear, non-time constant frequency dividing principle of the invention may be embodied in other forms such as illustrated in Figs. 2, 3, and 4.

In the circuit of Fig. 2, a source I30 of variable frequency supplies impulses through a. condenser C8, conductor 42 and rectifier diodes 44 and 46 to a condenser CIO, in the same manner as previously described with reference to Fig. 1a.. In this circuit, however, the charge on the condenser CIO affects the voltage at the plate I32 of a Thyratron type of gaseous discharge tube I34, which may be, for example, of the 885 type. The condenser CI is coupled to the plate I32 through a small inductance LIB and protective resistor R36. The grid I35 of tube I34 is connected to a biasing voltage source, indicated as a terminal -9 v., through a protective resistor R31, but the grid is not utilized for control purposes, the 885 type tube being utilized merely as a gas discharge diode tube. A cold cathode gas diode might be substituted for the Thyratron I34, but the latter is preferred because of its high degree of stability. In the case of the Thyratron I34, the heated cathode I30 thereof is connected to ground, and the positive signal from the rectifier diode 46 is impressed upon the plate I32. If, however, a cold cathode diode is used in place of the Thyratron I34, either the positive or negative pulse from the rectifier tubes 44, 46 may be impressed upon one plate of the diode.

As soon the condenser CIO has accumulated a sufficient potential to cause ignition of the Thyratron I34, the latter will discharge the condenser CIO substantially to ground potential. The signal thus produced in the primary I40 of an output transformer T6 may be utilized to provide a signal one half that of the source I30 to a conductor I42, and may also be utilized as an input for an amplitude limiting pentode 5B of a second frequency dividing stage.

In principle, the operation of the circuit of Fig. 2 is the same as that shown in Fig. 1a, since the condenser CIO is incrementally charged through the condenser C8 to a value such that it causes an amplitude responsive discharge apparatus, in the form of the Thyratron I34, to function. It will be noted that in the circuit of Fig. 2, just as in Fig. 1a, there are not circuit elements associated with the Thyratron I34, which provide a time constant comparable to the period of the signal. Thus, this gaseous discharge frequency divider is unlike the usual gaseous discharge relaxing oscillator type frequency divider in that all circuit functions are initiated solely by the signal, and thus the controlling frequency plays no part in the frequency division ratio.

In Fig. 3, the circuit includes the variable frequency source I30 and rectifying circuits similar to those of Figs 1a and 2. The positive pulses of the rectified input signal are thus accumulated on the condenser CIO, one terminal of which is connected to the plate I42 of a triode I44, such for example, as the 6J5G type. The grid I46 of the triode I44 is connected through a series grid resistor R40 and a grid resistor RM to a source of biasing potential indicated as a terminal I41. The cathode I48 of the triode I44 is connected to ground. The output of the triode I44 is coupled through a condenser CI2 to the grid I50 of a triode I52, the grid I50 being connected to a suitable biasing potential source through a grid resistor R42. The plate I54 of the triode I52 is connected to a suitable source of plate voltage indicated as a terminal +300 v. through a load resistor R44. The plate I54 is also connected through a feedback condenser CI4 to a terminal I49 intermediate the resistors R40 and RM, The output of the triode I52 is coupled through a blocking condenser CIE to the input of a current limiting pentode 56 corresponding to the tube 56 in the previously described circuits.

The circuit of Fig. 3 operates to divide the frequency of the source I30 in the following manner: As the condenser CIO attains a charge sulficient to cause the triode I 44 to start to conduct plate current, such conduction is rapidly increased to effect a substantial discharge of condenser CIO by virtue of the fact that tube I 52 serves as a phase inverter to provide a signal of positive polarity through feedback condenser C'It-to the g'rid I 46, th-us increasing the plate current-or tube l ll until condenser CIO is discharged and further-increasein positiveness of the'grid I46 has no effect. "In practice, this'dis- "charge takesplace in an extremely short spaceof time compared to the frequency of the source I30. Thus, thecircuit of Fig. 3 corresponds to i that of Fig-dd, it being noted, however, that the I phase inversion in the grid circuit is accomplished through the triode' I52 in "the circuit ofFig. 3,

Whereas in the circuit of Fig. 1, this phaseinversion is accomplished through the use of the tertiary winding L3-of the transformer T2.

A further modified form "of frequency dividing circuit which does nothave any frequency reso nantor timing constants associated therewith, but which instead has its operation controlled solely by the application of impulse of the frequency to be divided, is shown in Fig. 4., In this --.figure a pair of Thyratrons I60, IGI, have their" grids-I62, I63 connected to the'sour'ce I30 through blocking and decoupling condensers CI8 and CIS respectively. The grids'I62; I03 arecon'nected to a'suitable source of biasing potential indicated as a terminal -17 v. through grid resistors R50 and RSI respectively. Protective resistors R52 and R53 may be provided for the grids I62 and The plates I66 and IE1 of the Thyratrons I60 and IIlI are respectively connected to a suitable plate currentpot'ential source indicated as terminals +170 v. through load resistors R54 and R55, as wellasthroughlow va'lue protective resistors R56 and R51 respectively. The plates I60 and I! are coupled through a relatively large condenser C20. The cathodeI68 of the Thyratron ISO-maybe connected to ground, while the cathodeIGS of the Thyratron I6I may be connectedito ground through a' resistor R60 across which an output signalmmay be derivedthr'ough a blocking condenser C2I,-- such signal being impressed upon the grid of. a limiting pentode 56,

operating as previously described.

In the operation of the dividing circuit of Fig. 4, 'signal' pulse from the source I30 is simultaneously-impressed upon-the grids I62 and I03. However, due to unavoidable difierence's' inthe parameters of these tubes and thecircuit elements associ'atedtherewith, only one of these'tubes is 'renderedconductive, and the other tube is' im- Inedi'ately prevented from reaching a discharge c'ondition'because of the following factors. Assume that upon impressing a positive pulse from the source I30 upon the grids of these tubes, the gas of the tube I00 ionizes. The resultant plate current flow in this tube lowers the potential at the junction H0, and hence upon the junction I II, sufficiently to lower the potential on the plate Nil below the ignition point for a period of time in excess of the deionization time, but still small by comparison with the period of the frequency being divided. Thus, if the tube IEI was ionized at the time that the positive impulse was impressed upon its grid, it will be deionized.

Such conditions will continue until the next positive pulse from the source I30 finds the grid I02 in an already ionized gaseous discharge path between the cathode I68 and plate I50, and thus has no control. However, the pulse impressed upon the grid I63 is effective to cause ionization to occur in. the tube IBI and thus lowers the potential at the point Ill, and correspondingly the potential at the point I10, to the deionization point of the tube I60. This cycle is repeated with each alternate positive pulse from the source "'shape, 'will have a frequency one halfthat of the source I30.

, It will be noted that this output or quotient rrequenc is not dependent upon any time constants of the elements associated with these tubes I60, IGI; and thatthe alternate discharge of the tubes I00 and I 6| is controlled solely by the application of the controlling signal from the source I30. Thus, this apparatus is effective to divide the frequency of the source I30 over a very substantial range of the audio frequency spectrum, such as 4 or 5octaves.

The divider circuit of Fig. 4 differs fromthose of Figs. 1a, 2 and 3' in that it iscapable of division -only by thefactor of 2, whereas the circuits of Figsvla, 2 and-3 are capable of dividing by any integral divisor factor. ''However, all of the divider circuits-disclosed hereinhave the distinguishing feature that all of their voltage, current,

-- and polarity changes'resp'ond-only upon the application' of acontrollingSignalQwhich is not the case, for instance, of controlledrelaxation devices or the like.

While I have sho'wn and described a particular embodiment of 'my invention it will be apparent to those skilled-in the art that numerous modifications and variations maybe made in the form and construction thereof, without departing from the more fundamental principles of'the invention.- I therefore desire, by-the followingclaims, to include within the scope'of my invention all I such similara'nd modifiedforms of the apparatus disclosedyby which substantially the results of the'invention may be obtained by substantially the same or equivalent means. I claim:

T 1. In an*electrical--musical instrument having an output system including electroacoustic translating means, the combinationof an electrical pulse signal generator of dividend frequency, a plurality of playing keys, means operable by said keys for selectively tuning said generator to an audio frequency related to the nominal pitch corresponding to :the operated key, a frequency dividing circuit-containing a negative reactance frequency divider element, a non-linear electron discharge device coupled to said negative reactance element.-a coupling between said pulse generator and'said' electron discharge device such that all potential changes and polarity reversals on said frequency dividing negative reactive element are initiated solely by the application of said signal, said frequency dividing circuit thereby producing a quotient frequency related to said dividend frequency by an integral divisor, said divisor remaining a constant over a wide audio frequency spectrum exceeding one octave of dividend input frequency, signal collecting means for said pulse signal generator, signal collecting means for said frequency dividing means, and selectively operable means coupling either or both of said signal collecting means to the output system of the instrument.

2. In an electrical musical instrument having an output system including electroacoustic translating means, an adjustable frequency oscillator, key actuated means for determining the frequency at which said oscillator operates, means coupled to the oscillator and controlled solely by the number of electrical impulses produced by said oscillator to produce a rectangular wave impulse for every second impulse provided by said oscillator, and a tone quality controlling transmission circuit coupling said means to the output system of the instrument.

3. In an electrical musical instrument having an output system including electroacoustic translating means, the combination of a source of electrical impulses of variable frequency, playing keys operable to determine the frequency of the impulses derived from said source, means to convert said impulses into electrical pulses of uniform amplitude, means to accumulate said pulses, electrical discharge means responsive to the accumulation of a predetermined number of said pulses by said last named means to cause the discharge thereof, and means coupling said discharge means to said output system.

4. In an electrical musical instrument having an output system including electroacoustic translating means, a variable frequency source of electrical impulses of uniform amplitude, a plurality of playing keys, means operable by said keys to vary the frequency of said source, means for accumulating the electrical charges of said impulses, a device responsive solely to the total charge on said accumulating means to cause rapid discharge thereof, and means for coupling said device to the output system of the instrument.

5. In an electrical musical instrument having an output system including electroacoustic translating means and having a pedalboard comprising a plurality of keys, the combination of a pair of oscillators, circuits completed upon depression of two or more of said keys to tune one of said oscillators to a frequency related to the pitch corresponding to the lowest of the depressed keys and to tune the other of said oscillators to a frequency related to the pitch corresponding to the highest of the depressed keys, separate means for dividing the frequencies of the signals produced by said oscillators to produce sub-multiple frequency signals, and tone control circuits for coupling said last named means to the output system.

6. In an electrical musical instrument, means for dividing the frequency of a source of constant amplitude electrical impulses comprising, a rectifier, reactive means coupling said rectifier to the source of impulses, a charge storing condenser coupled to said rectifier to receive the output thereof, and relaxation means efiective to discharge said condenser whenever the potential across said condenser exceeds a predetermined value.

7. In an electrical musical instrument having an amplifying and electroacoustic translating system, the combination of a tunable variable frequency signal generating oscillator, a plurality of playing keys, means operated by said keys to vary the tuning of said oscillator and to cause it to oscillate at a frequency related to an operated key, a pair of similar electron discharge devices, each comprising an input and a plate circuit, and cathode, grid and plate electrodes, means intercoupling the plates and grids of said devices, means for coupling the output of said oscillator to the input circuits of both oi. said devices, said couplings between the plates and grids of said devices being arranged to cause voltages on said electrodes of value to materially reduce plate current flow in one of said devices upon an increase in the flow of plate current in the other of said devices and vice versa, whereby said devices will alternately be rendered of increased conductivity upon receiving successive signal impulses from said oscillator and produce a wave in the plate circuits of each of said devices comprising substantially solely a fundamental of one-half the frequency of said oscillator and a musically desirable series of odd harmonics of said fundamental frequency, and means for selectively coupling one of said devices or said oscillator, or both, to the amplifying and electroacoustic translating system.

JOHN M. HANERT.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,203,432 George June 4, 1940 2,254,284 Hanert Sept. 2, 1941 2,276,390 Hanert Mar. 17, 1942 2,039,119 Schlesinger Apr. 28, 1936 2,047,533 Von Ardenne July 14, 1936 2,284,101 Robins May 26, 1942 2,185,635 Kock et a1. Jan. 2, 1940 2,158,285 Koch May 16, 1939 2,305,625 Lauer Dec. 22, 1942 2,331,986 Lauer Oct. 19, 1943 2,349,810 Cook May 30, 1944 2,310,105 Michel Feb. 2, 1943 2,113,011 White Apr. 5, 1938

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