US1901986A - Electrical music system - Google Patents

Description

March 21, 1933. R, H. RANGER ELECTRICAL MUSIC SYSTEM Filed Nov. 28, 1931 Patented Mar. 2l, 1933 UNITED STATES PATENT OFFICE RICHARD HOWLAND RANGER, OF NEWARK, NEW JERSEY, ASSIGNOB TO RADIO CORPO- RATION OF AMERICA, A CORPORATION OF DELAWARE ELECTRICAL MUSIC SYSTEM The present invention relates to an electrical music system for producing musical sounds of Various qualities from electrically generated energy so controlled as to represent after predetermined selections various notes containing fundamental and harmonic frequencies for each note in musical selection.

The present application forms a continuation in part of my copending application Serial No. 417,466, filed December 30, 1929. The aforesaid application covers broadly the production of musical sounds and embodies a system wherein different frequencies corresponding to each of the several notes of a musical keyboard are generated electrically and then so controlled as to reproduce, when selected by an appropriate selector system, any desired musical composition. It has been determined -through experiments and practice that musical systems of this type operate substantially better when each note of the several reproduced simultaneously is carried in aseparate amplifier. Consequently, my above mentioned copending application provides for so selecting the various generated frequencies that frequencies corresponding to the fundamentaly and selected harmonics of each note are reproduced or ampliied through only a single amplifier, and then these amplified tones or frequencies may then be transferred to a suitable load circuit such as a sound re roducer or a wire line. In order to avoid o jectionable effects from clicking and the like, provision has been made to render the amplifiers operative only after the frequencies corresponding to the fundamental and selected harmonics have already been impressed upon the amplifying circuits. These general characteristics apply equally well to the present invention which is directed principally to the amplifying system and the manner of producing in the amplifying system different quality effects.

The fundamental object of the present in vention is to develop ways and means by which the usual thermionic amplifier system may be made to produce output energies of characteristics which, when reproduced by suitable sound translating or reproducing apparatus, represent quality 'effects simulating the percussion type of instruments. Due to the fact that the percussion type instrument has a changing output characteristic, it has in the past been difiicult to represent this type of instrument electrically. However, I have found that it is possible through the control of the Voltage applied to the amplifying system to control the amplifier in such manner that the output thereof rises and falls at a ratecorresponding to and simulating well known percussion` instruments.

In order to illustrate and explain the present invention recourse will be had to three different types of ercussion instruments which will serve as lllustrative examples of all such types of instruments. Therefore, in this specification reference will be had principally to the piano, mandolin and vibraphone effects, although it is to be understood that other similar effects may be produced in similar manner, and the disclosure should, therefore, be construed broadly as covering all such types of instruments generically.

Still other objects of my invention are to produce the percussion type effects in electrical music instruments without any complicated electrical switching arrangements and to` arrange the system so that it will respond instantly to the operators choice of quality effects as may be controlled by the usual tilting tablets or push buttons arranged on the console of an organ, for example, to enable the operator or organist to select the quality effect desired.

Still other objects of the invention are to provide in a simple manner an arrangement for producing the percussion effects which is relatively simple in its construction and arrangement of parts, a system which is substantially fool-proof, which will not require any great attention on the part of the operator, and which may be combined with electrical organs of the general type disclosed in my above named copending application with a minimum expense. c

Still other and further objects of the invention will become apparent and at once sug` gest themselves to those skilled in the art to which the invention relatesv by considering the following specification and claims in connection with the accompanying drawing, wherein:

Fig. 1 represents a suitable form of amplifier for amplifying generated electrical frequencies corresponding to a single note to be played at any instant; and,

Figs. 2-A, 2-B and 2-C represent a series of curves plotted with intensity against time to represent the output from the amplifying system for different quality effects. Of this group Fig. 2-A represents the piano effect; Fig. 2-B represents a Vibraphone effect; and Fig. 2--C represents a mandolin or pick instrument effect.

Now making reference to the accompanying drawing, and considering the same as representing only a single one of a number of amplifiers necessary to produce a number of musical sounds simultaneously, as Wasdis-` closed in my aforesaid copending application, the various reference numerals correspond for the most part to identical reference numerals in the original application in order to permit ease of understanding the present invention. It should, however, be borne in mind that the amplifying system herein represented will produce only one note including the fundamental and selected harmonies at any instant,

and for the production of .a complete'series p of notes simultaneously played the entire system shown herein would have to be duplicated a number of times, for example', six to twelve times, depending upon the number of notes it is desired to reproduce simultaneously.

- By t-he acco-mpanying drawing, conductors 115, 116, 117, 118 and 119 connect the amplifying system with suitable tone selection relays which in turn are connected to a source of tone frequency energy (not shown) The energy impressed upon the various conductors 115 through 119 inclusive is then transferred through suitable transformers 140, 141, 142, 143, 144 and 145 to a thermionic amplifier system comprising a plurality of thermionic amplifying tubes 153, 154, 155,

. 156, 157 and 158 having their outputs connected in parallel. To cont-rol the intensity of the various frequencies impressed upon the amplifiers, a number of resistor elements 146, 147, 148, 149 and 150 has been provided in series with the primary Winding of each o f the transformers 141 through 145 inclusive.

In the present instance, let it be supposed that amplifying tubes 153 and 154, as energized through transformers and 141 respectively, are used for the purpose of amplifying the fundamental frequency. In this instance it should be noted that transformer 140 impresses the fundamental with full strength or amplitude upon the amplifying tube 153, Whereas the transformer 141, for example, impresses the same fundamental frequency upon the amplifier 154 in reduced intensity, so that the net amplification may be some value greater than unity where desired. Similarly, transformers 142 through 145 inclusive, as controlled by resistors 147 through inclusive respectively, impress the various selected harmonic frequencies with controlled amplitudes suitable for representing the desired quality effects upon the amplifiers through 158 inclusive. The primary windings of the transformers 140 through 145 inclusive are'suitably grounded through conductor-'151 connected to ground at 152 in order that only a single Wire system may be necessary to impress the various tones upon the input of the amplifier. To control the amplification in desired manner, suitable biasing means such as the C batteries 159 may be connected in the input circuit of each of the amplifiers 153 through 158 inclusive. The filaments of the amplifiers may be supplied with energy through the variable resistor elements 163 Which connect with lthe positive terminal of the source of filament energy, and the opposite terminal of the filament may be suitably grounded at for example.

As was above stated, amplifiers 153 through 158 inclusive have their outputs con'- `nected in parallel through a conductor 166 connected in series with a choke to a ter minal 164 of positive potential +B suitable for energizing the plate electrodes of each tube. In shunt with the choke coil is a condenser element 168 and the primary Winding 169 of a transformer 170 to the secondary Winding 171 of which is connected a pair of ther- mionic amplifiers 172 and 173 in push pull. Each of these amplifiers may be biased in any suitable manner by means of a bias battery such as 174, and the filaments thereof may be connected to ground, for example, at 17,5. The output energy from the push pull amplifiers 172, 17 3 may be then transferred through the primary Winding 194 of transformer 195, and then picked up in the secondary Winding 198 of the transformer. To supply plate potential to the amplifiers 172 and 173, a connection is made to the midpoint 193 of the primary Winding 194 of the transformer. It is at this point that the con'- trol effectA for producing the various qualities to represent the percussion instruments will be introduced, but for the purpose of completing the description of the manner in which the tones as amplified are transferred to the load or utilization circuit the remaining portion of the amplifying system will first be described, after Which the manner in lli) which the various quality effects are produced In a manner similar to that ex lained with the preceding stage of push pul amplification, the input circuits of these amplifiers may be suitably biased by means of resistor 205 and biasing battery connected thereto. The filament circuits of these amplifiers may be supplied from a source of heating current connected to one side of the filament at 208, and to the other side of the filaments through potentiometer 207 and then to ground as at 209. The output energy from the amplifiers 199 and 200 is'then fed through a pair of conductors 242 and 241 to the primary winding 243 of a transformer 244, from the secondary winding 246 of which the useful amplified output is connected with a load circuit connected at terminals 247 and 248. This load circuit may be the usual type of sound reproducer in the event that it is desired to hear the music produced locally, or where it is desired to broadcast the produced energy, the terminals 247 and 248 may connect directly with a transmitter for transmission over wire or radio circuits, or the terminals may connect with any suitable form of land line to carry the energy to the point of transmission.

In my aforesaid application Serial No.

' 417,466, the desirability of connecting the tones for reproduction with the amplifying system prior to the time when the amplifier was rendered operative was explained, and. in addition, the aforesaid application disclosed ways and means by which the amplifier system was rendered operative immediately after the tones had been impressed thereon. NOW, according to the present invention, the same general features hold true. However, in the original case, the amplifiers were rendered inoperative by a removal of the plate potential therefrom at all times except When tones were keyed in the input circuit, and it was only at these times that the amplifier could function in the normal manner. According to the present application, instead of having the platesupply energ disconnected except when the tones are keye the plate supply connected to theterminal 184 is normally connected'todthe plates of the push pull connected amplifying tubes 172 and 17 3 through the armature 203 of the relay R40 resting against the contact 187 and connecting through a conductor 188 to the conductor 210 at a point 630. It will be seen that with the relay R40 unen'ergized, due to the lack of any impressed voltage being impressed thereon through the line 177 which connects with the keying contact of the selector system, the plate supply energy is then grounded through a conductor 189 connected to the armature 201-of the relay R40 and grounding through a resistance connection between the ground point and the contact 627 ofthe relay R40. Therefore, While plate potential is being supplied to the tubes 17 2 and 17 3, they are nevertheless maintained in an inoperative state as in the aforesaid applicaion.

Now sup ose that a note of the ke board is depresse ener 'from a suitable eyin contact of the se ector relays (not shown? is supplied through conductor 177 so as to flow through the terminal point 178, the conductor 179 to the armature 202 of the relay R40 from whence it passes through the contact 180 and the conductor 181 through the relay winding R40 and thence to ground. As soon as the relay Winding R40 becomes energized, all of the armatures 201, 202 and 203 1mmed1ately move to the left from the position shown, and the contact between the armature 202 and the terminal 180 is at once broken. However, when this happens, the same energy that was supplied through the conductor 177 then flows from the terminal 178 through the resistor 188 and the conductor 181 through the winding R40 to ground, so as to form a holding current just suicient to maintain the relay armatures 201, 202 and 203 over against their left side cgntacts or in the opposite position from that s own.

To provide a suitable arrangement bywhich late potential may be supplied to the tubes l 2 and 173, itis proposed to arrange the relay armatures 201, 202 and 203 in such a manner that when the relay R40 becomes energized the armature 201 will be first to open. This will then remove the ground' from the lead 210 and permit the plates of the tubes 172 and 173 to receive normal plate potential supply through the armature 203 and the contact 187 as supplying energy to the conductor 210 through the line 188. The operation of the armature 201 to occur first may 4be provided in any suitable manner, for example, by merely bending-the armature 201 slightly so that it leaves its contact 627 prior to the time when the armatures 202 and 203 become disengaged from the contacts 180 and 187 respectively upon energization of the relay R40.

Now, a very short time interval after the opening of the armature 201, the armature 203 also opens and the +B voltage supplied from the terminal 184 reaches the tubes 172 and 173 through a point 626 connecting through conductor 626 to the contact terminal 619 of the relay R40, and through the armature 612 of this relay the plate potential supplied at the terminal 184 is directed through the conductor 210, the choke coil 197 to supply the plate potential in the usual manner, assuming, of course, that none of the special quality effects which form the basis of this invention are desired. With the relay R40 so adjusted as to provide the seuence of operation above set forth, the conensers or capacity elements 600 and 625 may be fully charged before they are used to supply the plates of the tubes 17 2 and 17 3 with venergy in a manner to be hereinafter described.

Assume now, for example, that a piano effect is desired from the system. This e'l'ect 5 has been represented in a general form graphically by Fig. 2-A, wherein, when `plotting intensity against time, 1t 1s seen that the tone immediately rises to a full value and then fades out in a manner quite characterl0 istie of the usual piano. When the piano effeet is desired, the switch 624 serving to represent a tilting tablet or push button on the organ console is closed and this then causes the relay R46 to become energized by a flow of current from the switch 624 through the relay, and, as this happens, the armatures 611 and 612 move to the right from the position shown. This serves to break the contact already established between the contact point 619 and the armature 612 'so as to interrupt the supply of plate potential-from the source 184 to the tubes 172 and 17 3. In the first momentary connection of the plate supply for the tubes 172 and 173 from the point 184, the capacity element 600 will become ycharged through the conductor 188, the contact polnt 630, the conductor 210, the relay armature 610, the contact 618 connected to the armature 606 of the relay R43 and the contact 613 connecting to one side of the capacity element 600. lVhen the plate supply is disconnected following the opening of armature 203 at a time when the relay R40 is energized by the depression ofa key caus- 177, as above explained, the capacity element or condenser 600 then takes over the task of supplying plate potential to the plates of the tubes 172 and 173.

As will be appreciated, there is a logarithmically decaying voltage supplied to the plates of the tubes 172 and 17 3 through the contact 613, the armature 606 of the relay R43, through contact 618, through armature 610 of the relay R45, and thence through the conductor 210 to the plates. The tone produced from the push pull connected amplifiers172 and 173 thus fades out in amanner characteristic of pianos.

The usual type of percussion effect, such as the vibraphone eifect, may be produced in a manner quite similar to the piano eilect by closing, for example, the tilting tablets or switches 622 and 624 simultaneously, bearing in mind that the piano eiiect as produced by the switch 624 is used jointly with a second effect produced by operation of the switch or tilting tablet 622. Through the closure of the switches 622 and 624, relavs 11 and R46 respectively become energizedy by a flow of current therethrough from the switch element to the opposite side of the relay, and thus cause the armatures 602 and 612 respcc tively to be moved to the right from the position shown y ing current to'flow through the conductor of current in a manner already explained in y my above named copending application. In the aforesaid copending ap lication, a rubber tube arrangement was il ustrated for periodically decreasing the value of the plate potential supplied, and also there was disclosed a system for varying the filament current supplied to the tubes so that, in each instance, the output of the amplifying tube system was varied between certain predetermfned limits at al chosen rate.

Assume now that theconductor 626 oonnecting with the armatures 602 and 604 of relays R41 and R42 respectively is supplied with energy or pulsations of currents from a tremolo device, so that the current flow therethrough rises and falls in intensity at a suitable rate. As the relay R,u has been ener-- 'gized to move the armature 602 to the right from the position shown by the closure 'of the l switch 622, the fluctuating current supplied from the tremolo through the conductor 626 then passes through the contact point 614 to the relay winding RA13 so as to close the armatures 605 and 606 respectively over against their right side contacts from the position shown. at arate corresponding to the, tremolo rate, and thus alternately break the conta-ct between the armature 606 and the contact point 613.

Assume now that a note on the keyboard has been played and. that the capacity or condenser element 600 is energized as above explained for the production of the piano effeet. During the periods when the relay R43 is open (the position shown), the diminishing charge` on'the capacity element 600 supplies the plate energy for the tubes 172 and 173 as before, but during those periods when t-he relay .R4G is energized, the connection is broken at the Contact point 613 and the plate potential is then supplied only from the charge on a much smaller plate filter c'ondenser 197. lThis is illustrated graphically by Fig. 2-B, wherein, through plotting intensity against time, it is seen that the output rises to a. substantial peak, then decays lvery gradually, then more sharply, after which it rises again to a predetermined point, after which the same process is repeated. The tone thus produced in the load circuit or utilization circuit connected to the output terminals 247 and v248 of the system follows the characteristic vibraphone curve.

A mandolin elect may be produced in the system in a manner closely analogous to that already explained except to produce this effect the switches or tilting tablets 623 and 624 are closed simultaneously, so as to cause the relays R42 and R48 respectively to move the armatures 604 and 612 to the right from the position shown. As is seen from the drawing, the relay amature 603 when moved over against its right side contact will have positive energy connected to the right Side contact as indicated by the plus sign dlrected through itand the conductor connecting with the relay R,5 so as to cause this relay to become energized and move the armatures 609 and 610 respectively to the right from the positionshown so that they rest upon the right side contacts 620 and 617.

Similarly, as the armature 604 has been moved to the right over against the right side contact 615 by the energization of relay R42 through the closure of the switch or tilting tablet 623, the same pulsations of tremolo current above explained in connection with the Vibraphone effect are supplied through theconductor 626 to the relay armature 604 and through the contact 615 cause the relay R,4 to become energized periodically so as to vibrate the armatures 607 and -608 at a rate corresponding to the tremolo rate. As the armature 608 vibrates at the tremolo rate, contact is periodically broken with the contact point 615 and made with the contact point 616, and vice versa.

During the periods when the relay R44 is open, the plate Y of the capacity element 625 may receive a positive charge from the source of plate potential connected at 184 through the point 626, the conductor 626', the contact point 619, the armature 609, the contact point 620, the contact 615 of tle relay R44 and the armature 608 thereof. However, when the relay R44 is closed, on the other hand, the capacity element 625 is short-circuited through the armature 608, the contact 616 connecting to the opposite side of the capacity element so as to cause a positive 'charge on the plate X. v

Now, after a note has been played and the direct positive connection to the plates of the tubes 172 and `173 broken, the plate X of the capacity element 625 will, during those periods when the relay R44 is open, supply the plates of these tubes through the contact 617. the relayT armature 610 and the lead 210, with positive potential. During the periods when the relay R44 is closed, the plates of the tubes 172 and 173 will be maintained at positive potential by means of the filter condenser 197 connected in series with the lead 210 while the potential of the plate X of the condenser 625 is restored by connection through the armature 608 yand the contact 616 to the plate Y thereof, which has, of

course, been maintained at positive plate p0- tential during the periods when the relay R44, is open. The. effect of this alternate control of the plate potential by means of the capacity elements 197 and 625 is to produce a voltage upon the plates of the tubes 172 and `173 which produces in the utilization circuit connected to the terminals ,247 and 248 of the system an output varying as indicated by the intensity-time curve shown by Fig. 2-C.`

From the above, it is quite apparent that with a system of the type herein disclosedcapacity elements have been associated with the output circuits of a plurality of amplifiers in such a manner that, by the application of definite voltages as supplied from a voltage source used to supply the plate potential for the amplifiers, they function when a key of the system is depressed to break the complete connection instantly in such a manner that the amplifier only works from plate current in thc condensers which can be dissipated logarithmically in such a manner as to produce the effect desired.

By the above description, it should be recognized, of course, that applicant has made no effort to show a complete system, but for a practical instrumentality it should be understood that the entire arrangement herein disclosed is duplicated for a series of independent and separate amplifiers. Of course, to simplify the arrangement, there is preferably only a single tilting tablet or switch such as 622, 623 or 624 for the entire system, and these may be made to work separately for all amplifiers. Furthermore, where desired of course, it is possible to construct the system so that the various amplifiers may be provided with different quality effects, and in such cases it is desirable to have the different switches for the production of the different quality effects Work independently. Also, for the purpose of controlling the tremolo strength, I have provided a pedal connection which serves to vary the resistance 629 between predetermined limits, .and thus to control the strength of the useful tremolo effect as supplied through the conductor 628.

From the above description it will be apparent that many modifications and changes may be made without departing from the spirit and scope of the invention, and therefore I believe myself to be entitled to cover any and all of thcse'modifications as would suggest themselves to those skilled in the art to which the invention relates, and have therefore defined the invention in its broadest terms by the following claims, wherein I claim and desire to secure by Letters Patent of the United States the following:

1. In an electrical music system having electrical energy of frequencies corresponding to each note on the musical scale separately generated, the combination which comprises an independent amplifier for amplifying the electrical frequencies corresponding to each musical note to be reproduced, and means to supply operating voltages of predetermined varying values to each amplifier for varying the output energy thereof at a rate to cause the simulation of percussive instrument effects.

output energy thereof at a rate to cause the simulation of percussive instrument effects. 3. In an electrical music system having electrical energy of frequencies corresponding to each note on the musical scale separately generated,l the combination which comprises an independent amplifier for ainplifying the electrical frequencies corresponding to each musical note to be reproduced, and capacity means operatively associated with the output circuit of each amplifier to supply operating voltages of p redetermined varying values to eachampliiier for varying the output energy thereof at a rate to cause the simulation of percussive instrument effects.

4. In an electrical music system having enerating means for producing electrical requencies corres onding to each of the several notes throng out the musical scale, the

' combination which comprises means for independently amplifying the generated frequencies corresponding to each note to be reproduced, a utilization circuit for each of the amplified frequencies, and means for varying the strength of the amplified frequencies supplied to the utilization circuit in a manner to, simulate the rise and fall of audible energy from percussive instruments.

5. In an electrical music system having means for electrically generating, amplifying and audibly reproducing tone frequencies corresponding to ,the several notes throughout the musical scale, means for varying the intensity of the audibly reproduced tone frequencies between predetermined maximum and minimum intensities, said variation occurring at a relatively slowly changing logarithmic rate for changes between predetermined maximum and minimui'n intensities and at a rapidly. increasing rate for each change from minimum to maximum.

6. In an electrical music system having a series of alternators for producing electrical frequencies corresponding to the consecutive notesof a musical scale, a plurality of amplifiers for amplifying the various produced` frequencies'in accordance with a predetermined selection thereof, means for controlling the intensity of each of the frequencies impressed upon said amplifiers in accordance with the tone quality desired, capacity means associated with the amplifying systems for supplying definite voltages thereto during periods when each am liier is rendered operative and providing or a adual dissipation of energy from the ampli er during said lperiods, and a sound reproducer coordinate with each of said am lifying systems for converting the amplifie energy into audible ener 7 In an e ectrical music system havin a plurality of sources for generating electrical frequencies corresponding to the fundamental and other partial frequencies for each note throu hout themusical scale, the combination of a plurality of amplifiers each arranged to amplify at any instant the frequencies corresponding to a single note only, means for maintaining a portion of each amy plifier circuit during periods of inoperativeness at ground potential, means for keyin each amplifier circuit independently wit electrical frequencies corresponding to a. note to be reproduced thereby, and a lurality of relay means associated with t e arnplifier circuits for controlling the operative characteristics thereof to cause va fluctuating output therefrom which decreases in intensity logarithmically to simulate percussive instrument effects.

8. In an amplifying circuit for electrical music devices, a lurality of vacuum tubes serving to ampli y frequencies corresponding to the several ynotes on the musical scale, means for applying operating potentials to said amplifying circuit, capacity means associated with said supply circuits and adapted to become charged throu h the application of said potentials, a plurality of relay means for rendering said amplifiers operative in accordance with predetermined note selections, a second plurality of relays for controlling the quality effects from the output of the said amplifiers, said second series of relays being adapted to control the discharge of energy from said capacity elements to produce. a logarithmically changing intensity output from said amplifiers to simulate percussive instrument effects.

9. In an amplifying circuit for electrical music devices, a plurality of vacuum tubes serving to amplify frequencies corresponding to the several notes on the musical scale, H5

means for applying operating potentials to said amplifying circuit, capacity means associated with said supply circuits and adapted to become charged through the application of said potentials, a plurality of relay means for rendering said amplifiers operative in accordance with predetermined note selections, a second plurality of relays for controlling the quality effects from the output of the said amplifiers, said second series of relays being adapted to control the discharge of encrgy from said capacity elements to produce a logarithmically decreasing intensity output from said amplifiers to simulate percussive instrument effects.

10. n an amplifying circuit for electrical music devices, a plurality of vacuum tubes serving to amplify frequencies corresponding to the several notes on the musical scale, means for applying operating potentials to said amplifying circuit, capacity means associated with the potential supplying circuits and adapted to become charged through the application of said potentials, a plurality of relay means for rendering said amplifiers operative in accordance with predetermined note selections, a second plurality of relays for controlling the quality effects from the output of the said amplifiers, said second series of relays being adapted to control the discharge of energy from said capacity elements to produce a logarithmically changing intensity output from said amplifiers to simulate percussive instrument effects, and a tremolo control device for varying the supplied potentials between predetermined limits for causing during the periods when said ampliers are rendered operative periodic increases in the charges upon said capacity elements, whereby after predetermined periods of logarithmically changing intensity outputs the intensity of output is rapidly varied in an opposite direction for a repetition of the preceding intensity change so as to simulate percussive instrument effects.

11. In an amplifying circuit for electrical music devices, a plurality of vacuum tubes serving to amplify frequencies corresponding to the several notes on the musical scale, means for applying operating potentials to said amplifying circuit, capacity means associated with the potential supplying circuits and adapted to become charge-d through the .application of said potentials, a plurality of relay means for rendering said amplifiers operative in accordance with predetermined note selections, a second plurality of relays for controlling the quality effects from the output of the said amplifiers, said second-series of relays being adapted to control the discharge of energy from said capacity elements to produce a logarithmically decreasing intensity output from said amplifiers to simulate percussive instrument effects, and a tremolo control device for varying the supplied potentials between prcdetermined limits for causing during the periods when said amplifiers are rendered operative periodic increases in the charges upon said capacity elements, whereby after predetermined periods of logarithmically decreasing intensity outputs the intensity of output is raised rapidly for a repetition of the decrease in intensity soI as to simulate percussive instrument effects.

RICHARD HOWLAND RANGER.

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