US2543628A - Electrical musical instrument - Google Patents

Description

i Feb 27, 1/951 J. M. HANERT ELECTRICAL MUSICAL INSTRUMENT 2 Sheets-Sheet l Filed May l5, 1946 febfzz 1951 J M, HANERT 2,543,628

ELECTRICAL MUSICL INSTRUMENT Filed May 15, 1946 2 SheefS-Sheei 2 fnrev? for :fo/20 M15/Werf Patented Feb. 27,. 1951 UNITED STATES PATENT OFFICE ELECTRICAL MUSICAL INSTRUMENT John M. Hanert, yPark Ridge, Ill., assignor to Hammond Instrument Company, Chicago, Ill., a corporation of Delaware Application May 15, 1946, Serial No. 669,941

19 Claims. l Y

My invention relates generally to electrical musical instruments and more particularly to improved means for obtaining desirable tone intensity envelopes.

One of the distinguishing features of a musical tone is the character of its intensity envelope, that it, the manner in which the tone comes on and dies away or, more technically, the character of the attack and decay.

Several methods and means have been proposed to obtain desirable intensity envelopes for the tones produced by electrical instruments. One method was to provide a thermionic control tube for each key circuit, whereby depression of the key, through resistance-capacitance networks,

' controlled the potential on one of the electrodes of the tube so as to vary the gain thereof. Instruments having tone intensity control means of this character do not lend themselves Areadily to making changes in the character of the tone intensity envelope for individual notes of a sequence. In other words, the player cannot cause changes in the intensity envelopes of different notes by the manner in which he manipulates the playing keys.

Another method and means which has been proposed in the past for controlling the intensity envelopes of tones comprises the utilization of a gain controlling means, common to all the keys, in the output signal transmission system of the instrument, in which the gain of the transmission system is direct current controlled through a resistance-capacitance network by key-operated switches connected in parallel. In such apparatus, when keys are depressed in rapid succession in a non-legato manner, the tone controlled by the second depressed key will ordinarily commence sounding at substantially the intensity at which the tone controlled by the previously depressed key was sounding at the time the second key was depressed, and there is inevitably a certain amount of noise, frequently referred to as keythump or key click, introduced due to the distortion produced by the umnodulated D. C. component, even though the control is effected through balanced push-pull circuits. Y

The attack and decay apparatus of my invention differs from such prior systems and apparatus in that it does not have any unmodulated D. C. component and is predicated upon the idea that the envelope controlling means shall have the ability to re-set itself substantially instantaneously upon the release of a key, so that whenever the envelope effect is desired it may be Lobtained merely by-making certain that all previously depressed keys are released at the instant of depression of the key controlling the tone which is to have the desired attack characteristics of the tonal intensity envelope controlling means. To obtain the most desirable artistic effects, the tonal intensity envelope controlling apparatus should operate to re-set itself in an interval of time so short that the ear does not discern any denite break or interval of silence between successive tones. By the use of such apparatus of my invention the musician is able to obtain the very unusual and highly desirable tonal envelope characteristic without perceptibly breaking the legato continuity of the music being produced.

It is thus an object of my invention to provide an improved means for controlling the attack and decay characteristics of a musical tone signal.

A further object is to provide an electrical musical instrument in which the character of the tone intensity envelopes may be preselected, and in which the intensity of the tone may be made to vary automatically, following the depression of a key, in any one of a wide variety of different patterns.

A further object is to provide means for selectively changing the tone intensity envelope so that the tones may have fast attack and slow decay; slow attack and fast decay, or gradual attack and gradual decay.

A further object is to provide an improved circuit for operating a plurality of relays in a predetermined time sequence.

A further object is to provide an improved electromagnetically operated means for varying the degree of lcoupling between the output of the generating system of an electrical musical instrument and the input of the amplifier thereof, the coupling being adjustable to produce a tone having either rapid attack and slow decay, slow attack and rapid decay, or gradual attack and gradual decay.

A further object is to provide a unitary variable impedance envelope controlling means which shall operate on the common signal of all the keys of a keyboard.

Another object of my invention is to provide an envelope control signal transmission system in which true -chimelike tones may be produced in which the higher order partials may be made to decay more rapidly than the lower frequencies. It has been found that it is desirable to increase this rate of decay over and above what would normally be obtained through the use of the customary bass compensation circuits. By complex electrical reactive networks associated with the variable amplitude signal transmission apparatus, it becomes possible readily to simulate any rate of decay and to provide diiTerential rates of decay for different frequencies. For the production of true chimelike musical tonalities this is highly desirable.

Another object of my invention is to provide variable transmission envelope control means in which the rate of decay may be made variable during the decay time interval and may be made to coincide precisely with any `desired curve.

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

Figure l is a schematic wiring diagram of a portion of the output system of an electrical musical instrument showing vacuum tube operated relays for controlling the attack and decay characteristics of the tones;

Figures 2 and 3 are diagrams showing the various tone intensity Aenvelopes obtainable with the circuits and apparatus shown in Fig. 1;

Figures l and 5 are diagrams, partly schematic, showing modified forms of the invention; and

Figures 6, '1, 8 and 9 are tone intensity envelope diagrams of the type obtainable with the circuit and apparatus of Fig. 4.

In several types of electrical musical instruments such, for example, as that shown in the patent to Laurens Hammond, No. 1,956,350, there is no simple and convenient way for changing the intensity envelope of the tones produced. In instruments of this type the generators operate continuously to provide the various frequencies required, and upon depression of one or more of the playing keys, certain generators are directly connected to the output of the instrument by key-operated switches. Upon release of the keys the switches immediately open and disconnect the previously connected generators from the output circuit, As a result, both the attack and decay of the tones produced are abrupt, and in the rendition of some types .of music this kind of tone intensity envelope is not the most desirable.

Since in musical instruments having two manuals it will seldom, if ever, be desirable to provide means for controlling the tonal intensity envelopes of the 'tones controlled by both manuals, the invention is herein illustrated as applied to the output of a single manual, the manual being represented by a plurality of keys ID, each of which upon depression, in addition to controlling the transmission of the tone signal from the generating system to the output system, completes a circuit by closure of a switch l2. The various switches I2 are in parallel, and depression of any of the keys will complete a circuit from a conductor I4 through a resistor I6 Ato ground. By closure of other key operated switches (not shown) for the upper manual of the organ, indicated by a block i8, predetermined signal generators are connected to a conductor 26, the output signal appearing between the conductor 20 and ground.

The conductor I4 is connected to the grid 22 of a triode 24 through a grid resistor R26l of relatively low value. The grid 22 is also connected through a resistor R28 of relatively high value to actual practice the relays 30 and 3l may be combined in a single relay.

It will thus appear that, whenever one of the keys i0 is operated, the grid 22 is connected to ground through relatively low value resistors R16 and R26 so as to render the triode 24 conducting', and thus energize relays 30 and 3 l.

Upon energization of the relay winding 30 it opens a plurality of switches 42. One pole oi each of the switches 42 is connected through a conductor 44 to a terminal 45 of fixed negative potential. The other pole of each of the switches 42 is connected through a resistor R40 to the grid 4l `of one of -a plurality of triodes 32 to 38, the potential maintained on the conductor 44 being suiciently negative to bias these triodes beyond .Cuto

The relay winding 3|, upon energization, closes -a switch 46 which connects the grid 4l of the triode 32 to ground through a timing resistor R41 which is thus placed in parallel with a timing capacitor C48. Since the cathode of triode 32 is also connected to ground it will b e apparent that, when the switch 42 associated with triode 32 is open and its switch 46 closed, the potential on the grid 4i will increase gradually, at a rate de- -termined by the values of R41 and C48, until this tube becomes conducting. Plate current through this tube` then energizes a relay winding 50 which likewise closes a switch 46 connecting the grid of the next successive triode 33 to ground through a timing resistor R41 which is then connected in parallel with its associated timing capacitor C48. The time constants of the meshes R41 and C48 associated with the triodes 32 to 38 may be of any desired reasonable value to produce pleasing attack of the tones. The circuits of each of the triodes 32 to 38 are substantially identical although the values of R41 and C48 may vary from triode to triode to obtain the desired time delayg The relay 3l and relays 50 associated with the triodes 32 to 34, in addition to closing switches 46, operate switches 52 and 53. Each of these switches has one pole connected to the signal conductor 20. The switch 53 has its other pole connected through a resistor R54 and ,capacitor C55 with a conductor 6 0. The switch 52 is normally in a position to complete a circuit from the conductor 20 through a resistor R56 and capacitor C51 to conductor 6l, and when the relay is energized, the switch 52 connects the conductor 20 to a conductor 62 through a resistor R58. Conductors 60, 6l and 62 may be selectively connected to ground by operation of a three pole switch 64.

Each of the relay windings 50 associated with the triodes 35 to 3 8 inclusive, in addition to operating switches 46 and 52 closes a switch 66 which, when the relay is energized, connects conductor 20 to conductor 60 through a resistor R62, some of which may have ,capacitors C69 in parallel therewith. The signal on the conductor 26 is impressed upon the grid of a preamplifier triode 1u, the output of which is supplied to a power amplifier 12 coupled to a speaker 14.

The switches 53 and 66, and resistors R54 and R68, assuming that the switch 64 is positioned to connect conductor 60 to ground, are successively effective first to provide fewer and then additional paths througlrxl which the signal may be shunted to ground, and thus rst increase and then decrease the amplitude of the signal appearing on the grid of the preamplifier triode 10. These resistors are of such values that as their associated switches 53 and 66 are actuated. due to the successive operation of their relays 5D, the amplitude of the signal on the grid of triode is increased as the switches 53 are successively opened, and that the amplitude of the signal is decreased as the switches 66 associated with the triodes 35 to 38 are successively closed. Due to presence of capacitors C55 and C69, the rates of attack and decay for different frequencies will be atdiierent rates.

Resistors R54 and R68 have such values that the amplitude of the output signal will first increase and then decrease in substantially equal db steps, in the manner similar to that indicated by the curve L shown in Fig. 3, in which the ordinates are to a logarithmic scale. Thus the tone will have a rather gradual attack and gradual decay, Due to the provision of the capacitors C55, the higher frequencies will have a somewhat slower attack and faster decay than the lower frequencies. The higher frequencies will thus have intensity envelopes similar to the dotted line curve 15H of Fig. 3.

Operation of the relay 3I and the several relays 50 in their timed sequence, assuming the switch 44 is in position to ground conductor 6I, will successively disconnect attenuating resistors R513 and capacitors C51, and the amplitude of the signal appearing at the grid of triode 10 will therefore increase, generally in the manner indicated by the line curve 16 shown in Fig. 2. Due

to the provision of capacitors C51, the intensity envelopes for the higher frequencies will have a more gradual attack than the lower frequencies. If the switch 64 is in the position in which it is shown in Fig. 1, namely grounding the conductor 62, the operation `of switches 52 upon successive energization of the relay windings 3|, 50 Will successively connect the resistors R58 and the meshes R58-C59 in parallel between conductor 29 and ground. As a result, the amplitude of the signal appearing on the grid of triode 1D will decrease upon the successive operation of the relays, and the tone intensity envelope will have the general form illustrated by the curve 18 ofv Fig. 2, with the higher frequencies decaying more rapidly than the lower frequencies. The musical instrument is played in the usual manner, the musician iirst adjusting switch 64 to the desired one of its four positions. With the switch 64 in its dotted line position, the instrument may be played in a legato manner whenever the usual organ-like tonal intensity envelopes are desired. When, however, it is desired that the tones shall have intensity envelopes with either slow decay, slow attack, or medium attack Y and decay, the switch 64 will be correspondingly adjusted and the keys depressed in a non-legato or detached manner. Whenever any of the keys I0 are depressed the output of predetermined generators is impressed between the conductor 29 and ground. Depression of a key ID also results in the closure of its associated switch I2, I4, to connect the grid of triode 24 to ground and thus render this triode conducting. When the relay 30 is thus energized it removes the cutoff biasing potential from the grids of triodes 32 to 38 by opening the switches 42. Then in predetermined time sequence the triodes 32, 34 will be rendered conductive and will energize their associated relays 5D.

If the keys are depressed in a legato manner with the switch 64 positioned to ground one of the conductors 60, 6I, 62, the first key depressed will cause the resulting tone to have an intensity envelope similar to one of the curves of Figs. 2 and 3. Subsequently depressed keys will be sounded at a constant intensity the same as that of the nal intensity of the rst tone.

If the switch 64 is in position to ground conductor 62, the tones will have fast attack and slow decay and thus sound like chimes,`whereas, if the switch 64 is adjusted toI ground conductor 6I, the tones will have a slow attack as is characteristic of the wind instruments. If the switch E4 is adjusted to ground conductor 60, the tones produced will have gradual attack and gradual decay, such as is characteristic of the bowed string instruments. Whenever none of the keys of the upper manual is depressed, the triode 24 is immediately biased negatively beyond cutoff, so that plate current ceases and relays 30 and 3l are .deenergized Upon deenergization of relay 39 its switches 42 are closed, and a biasing potential of sufficiently negative value to Cut off triodes 32 to 38 is applied to the grids thereof, thereby promptly deenergizing all of the relays 50 and restoring the circuits to normal condition.

It will thus be clear that by adjusting switch 64 to its dotted line position, the usual sustained organ tones may be obtained, and that when the instrument is played in a non-legato manner,

with switch 64 in one of its other positions, the

tones may have intensity envelopes of any of the types represented bythe curves of Figs. 2 and 3, but that under the latter condition, the tones may be produced with constant amplitude intensity envelopes merely by playing in a legato manner.

While the invention is disclosed as making it possible to select only one of three different intensity envelopes for the tones, it will be clear that envelopes of different form might be obtained by providing additional switches such as 52, 53 and 65, connected by impedances of differ- 4ent values to an additional conductor similar to the conductors 69, ESI and 62. It will also be clear that the number of triodes 32-38, with their associated circuits, which are employed, may be varied to secure any desired number of gradational steps in the intensity envelopes. Furthermore the time intervals between operation of sucn cessive relays 5i! may be changed by changing the bias potential on terminal 45, or, by utilizing ganged, adjustable resistors R41 or adjustable capacitors C48, or both.

The invention may be embodied in a variety of different forms, such for example as shown in Figs. 4. and 5. In Fig. 4 each of the keys Io, upon depression, is adapted to complete a circuit through a solenoid winding 8U. This solenoid has a plunger 82 pivotally connected to a lever 84 mounted for pivotal movement at a pivot 85. The lever 84 has an arcuate capacitor plate 83 secured thereto and suitably insulated therefrom. The plate 88 is connected to key operated switches I I9 by a conductor 89. y

The plate 88 cooperates with capacitor plates 90, 9| and 92 which are connected respectively to contact points 94, and 96 of a switch 98, the movable contactor of which is adapted to make contact with the contacts 94, 95 and 95 separately, simultaneously with the contacts 95 and 96 or .94. and 95. The switch 98 is connected to the input circuit of a triode I 99, which includes a grounded capacitor C99, which operates as a phase splitting tube to provide a push pull output to a power amplifier |92, the latter being coupled to a speaker |64.

The speed at which the solenoid 8B may move .amaees the lever 84 is determined by a dashpot mechanism comprising a cylinder |08 and piston |08. A `piston rod |09 has `a pin and slot connection with the lever 1&4. The piston has a passageway provided with .a Vcheck valve I I0, this check valve operating `ina manner to permit free now of air from the upper end of the cylinder to the lower end thereof., but to prevent .flow in the reverse direction. -During the downward stroke of the piston V|08 air is discharged from the lower vend of .the 'cylinder |00 through a port l|,2, the effective size of which is `controlled by a needle valve I|4. it will thus appear that when the solenoid is venergized the lever 84 is swung counter-clockwise .at a rate determined by the effective size of the port ||2 but that when the solenoid is deenergized the lever will be swung very rapidly clockwise by a return spr-ing ||6 attached to the piston rod |09.

The tone signal generating means of the `musical instrument is indicated as a source of alterynating current I8 connected between ground and the capacitor plate S8 through key switches, indicated by the block |9 operated by the keys l0.

When the switch Q8 is adjusted to make contact with point S6, and a key I is depressed, the solenoid 80 swings the capacitor plate ES upwardly, at a rate controlled by the dashpct mechanism, into registry with the capacitor plate 92. Since the degree of coupling of the generators of the `musical instrument with the triode is dependent upon the capacitance between the plates 83 and 02, the amplitude of the signal transmitted to the amplier |02 will be increased substantially proportionately with the increase of the capacitance between plates 88 and $32. Thus the tone produced will have a gradual attack, as indicated by the curve of Fig. 6. When the depressed key is released the tone signal is immediately removed from the capacitor plate 38, and the latter will be returned rapidly toward its normal position since the dashpot will not have any appreciable effect. In order to secure maximum speed in the return movement of the capacitor plate 88 the arm 84 and the moving parts of the dashpot are preferably made of the lightest weight compatible with their necessary strength. The mechanism. will thus immediately be restored to its normal position, in readiness for operation upon depression of the next playing key.

If it is desired to produce tones having rapid attack followed by slow decay, the switch 98 is moved to contact with point 94 only. When a key is depressed under these conditions, the solenoid and dashpot mechanism will operate in the manner previously described, but since it is the capacitance between plates 88 and 90 which now is determinative of the amplitude of the signal transmitted, it Iwill be apparent that the tone will start at high amplitude and gradually decay, producing a tonal intensity envelope similar to those of plucked string instruments and chimes of the type indicated by the curve in Fig. 8.

When the switch 98 is made to contact with point 95 only the capacitance between plates 88 and 9| will determine the amplitude of the signal transmitted, and the intensity envelope will therefore be one of relatively slow attack and relatively slow decay, as indicated by the curve of Fig. 7.

When the switch 98 is made to contact with points S and 95 the attack will be relatively rapid followed by a partial decay of the tone. Similarly when the switch 98 is positioned to contact both points 94 and 95 the intensity envelope will be one which has va sharp attack and is followed 'by a portion of sustained amplitude and a subsequent gradual decay to a somewhat lower amplitude.

:Similar results may be obtained by .a construction such as shown in Fig. 5, in which the solenoid -80 :operates acam |20 of insulating material carried by an arm |22. A dash pot mechanism, comprising -a cylinder `121|., piston |26, and adjustable needle valve |29, is suitably connected to the arm |22. Thepiston |25 is provided with a passageway controlled by a check valve |28 which opens freely to ,permit flow of air from the lower to the `upper end of the cylinder |24, but prevents flow in the reverse direction. Thus as the solenoid is energized the .arm |22 will be swung counterclockwise at a rate controlled by the needle valve |29, and upon deenergization of the solenoid will swing clockwise at a rapid rate due to the force of the spring |30.

The insulating cam |20 is cooperable with a plurality of spring contact iingers |32 which normally make contact `with a grounded conducting plate |34. Each of the contact fingers |32 is connected by a resistor R|3 (representative of any suitable impedance element or mesh) to the out- A `put conductor |38 of the musical instrument generating and keying system |40. Thus when all ci the spring contact fingers |32 are in engagement with the plate |34, the generating system |40 is shunted by all of the resistors R|36, but as the arm 22 swings counter-clockwise and raises contact ngers |32 from the plate |34, these reeistors RNS are successively disconnected from the circuit, and the eiective amplitude of the signais provided by the generating system |40 and impressed upon an amplifier |42 is increased. Thus the tones will have intensity envelopes characterized by slow attack, such as represented generally by the curve shown in Fig. 9. When the key is released the arm |22 swings rapidly clockwise, but since the release of the key also cuts olf the signal from the generating system, the tone will decay abruptly. The spring contact fingers |32 and the cam |20 may be of any conventional construction, such for example, as disclosed in Hammond Patent No. 2,254,366, granted September 2, 1941.

Thus in each of the three embodiments of the invention the output signal controlled by the key operated switches has its effective amplitude envelope controlled in response to the depression of a key, in a manner to produce a tone intensity envelope of predetermined characteristics. While in the embodiment shown in Fig. 5 the only form of intensity envelope obtainable is that of gradual attack as indicated in Fig. 9, it will be apparent that by having the cam |20 so constructed as to successively bring the contacts |32 into engagement with the plate |30, the intensity envelope would be one of sharp attack and slow decay somewhat similar to that shown in the diagram of Fig. 8. Similar results could be obtained by making the cam of metal, connecting the cam to ground, and making the plate |34 of insulating material.

The underlying principle of all three embodiments is that the tone intensity envelope is predetermined, or preselected from one of a plurality `of predetermined available forms of tone intensity envelopes. The effectiveness of the tone 'intensity envelope changing means may, when the latter is adjusted for gradual attack, be rendered substantially ineffective by playing the keys in a legato manner and again rendered effective merely by changing the style of playing to non-legato, that is, releasing .all the depressed keys prior to depression of another key or keys. While the intensity envelope controlling meansis particularly effective in the rendition of solo or melody parts, it also has advantages in the rendition of chords when it is desired to simulate chimes or obtain similar tonal effects.

While I have shown and described particular embodiments of my invention it will be apparent to those skilled in the art that numerous modifications and variations may be made in the form and construction thereof, without departing from the more fundamental principles of the invention. I therefore desire, by the following claims, to include within the scope of my invention allsuch similar and modified forms of the apparatus disclosed, by which substantially the results of the invention may be obtained by substantially the same or equivalent means.

I claim:

l. In an electrical musical instrument having an electrical tone signal generating system, an output system, and playing keys for controlling the transmission to the output system of the electrical tone signals produced by the generating system, in combination, a plurality of tone signal attenuating means in the output system, switches respectively actuated by the keys, and means having its operation initiated by any of the key actuated switches and operable to render the plurality of tone signal attenuating means eiective in predetermined timed sequence.

2. The combination set forth in claim 1 in which at least some of the tone signal attenuating means comprise meshes having reactive 'elements of value sufficient to cause some audio frequencies to be attenuated substantially more than other audio frequencies.

3. The combination set forth in claim 1 in which the plurality of tone signal attenuating means comprises a plurality of meshes some of which include shunt capacitors of such values as to cause the attenuation of the higher audio frequencies to a greater extent than the lower audio frequencies.

4. The combination set forth in claim 1 'in which the means to render the signal attenuating `means effective includes means operative upon release of the keys rapidly to reset itself in condition for reoperation.

5. The comibnation set forth in claim l in which the signal attenuating means comprises a plurality of groups of signal attenuating meshes, and in which there are selectively operable means for conditioning one or the other of the groups for effective operation.

6. In an electrical musical instrument having playing keys, an output system, and a generating system; the combination of a solenoid, energizing circuits for said solenoid completed upon operation of any of the keys, and means operated by the solenoid to attenuate the output of the signal generating means in predetermined relation to time, thereby to produce a tone signal envelope of predetermined attack and decay characteristics.

'7. In an electrical musical instrument having a plurality of keys, electrical musical tone signal generating system, an output system, and means operated by the keys to couple the generating system to the output system, said last named means comprising a solenoid, circuits for energizing said solenoid upon depression of any of the keys, a variable attenuation means coupling the outputto the signal generating system to the output system, and means operated by the solenoid to Vary the degree of coupling effected by said coupling means, whereby the tone signals will be transmitted to the output system with predetermined attack and decay characteristics.

8. In an electrical musical instrumenthaving a keyboard comprising a plurality of playing keys, an electrical tone signal generator, an output system, and means controlled by the keys for transmitting an electrical tone signal representing musical tone from the generator to the output system; the combination of a switch for each of said keys, an electromagnetic device, a source of current, electrical'circuits connect-v ing said device to said source of current upon operation of any of said key switches, and means operated by said device to change the effectiveness oi the coupling between said generator and the output system at a predetermined rate to produce a predetermined tone intensity envelope for the musical tone signal transmitted to the output system under the control of a key.

9. In an electrical musical instrument having a` keyboard comprising a plurality of keys, vlvan output system, a tone generating system, and means controlled by the keys for transmitting to the output system tone signals produced by the generating system; a Vplurality of attenuating impedances in the output system, means for sucA` cessively rendering said impedances ineffective, a cam for operating the last named means, a solenoid for operating the cam, means controlling the speed of operation of the cam, and aplu rality of solenoidenergizing circuits respectively completed by operation of the keys. f

10. In an electrical musical instrument hav-l ing a keyboard comprising a plurality of keys, an output system, a tone generating system, and means controlled by the keys for transmitting to the output system tone signals produced by the generating system; a plurality of attenuating impedances in the output system, and means for successively rendering said impedances ineffective, comprising a plurality of switches, a cam for operating the switches in succession, solenoid for operating the cam, a dashpot mechanism controlling the speed of operation of the solenoid, and a plurality .of solenoid energizing circuits `respectively completed by operation of the keys. 11. In an electrical musical instrument having a keyboard comprising a plurality of keys,l an output system, a tone generating system, and means controlled by the keys for transmitting to the output system tone signals produced by the generating system; a plurality of attenuating impedances, some of which are initially effective to attenuate the signal appearing in the output system, and means controlled by the operation of any one of the keys successively to render the initially effective impedances ineffective and thereafter render other attenuating impedances effective to attenuate the signal transmitted to the output system.

12. In an electrical musical instrument having a keyboard comprising a plurality of keys, an output system, a tone generating system, and means controlled by the keys for transmitting to the output system tone signals produced by the generating system; a plurality of attenuating impedances in the output system, and means initiated by the operation of any of the keys to render said attenuating impedances successively to attenuate the output signal impressed on the output system.

13. In an electricalY musical instrument having a keyboard comprising a plurality of keys, an output system, a tone. generating system, and means controlled by the keys for transmitting tothe output system tone signals produced by the'generating system; a plurality of attenuating impedances in the output system, and means initiated. by the operation of any of the keys to render said attenuating impedances successively ineffectiveY tov attenuate the output signal impressed on the output system.

14; The combination set forth in claim 13, in which the means for rendering the impedances ineffective comprises a series of relays operated in timed sequence to open switches disconnecting the, impedancesA from the output system.

15. The combination set forth in claim 13` in which, the impedances. are connected in the output` system by switches, and; in which an electromagnetic device is effective to open` said` switches inv relatively slow succession upon depression of a key and to close the switches rapidly upon theirelease of thekey` 16, In an electrical musical instrument having a keyboard comprising a plurality of keys, an output system, a tone generating` system, and means controlled bythe keysV for transmitting-to theoutput system tone signals produced by the generating system; a cathode follower tricdeV in the output system, avariable capacitor forv cou.- pling thel output of the generating system tothe inputr of the cathode followery triode, and means controlled byr the depression of any of the keys to vary the effective capacitance ofI said variable capacitor at a predetermined rate.

17; Thecombination setforth in claim- 1,6 in which the means for operating. the variable capacitor comprises a solenoidenergizedby the depression of any of, thekeys, and theV meansfor determining the rate of` variation of the capacitor comprises an adjustable dashpot mechanism connected tov the solenoid for controlling the speed of operation thereof.

18. In an electrical musical instrument the combination of playing keys, a generating system for providing electrical signals` corresponding to musical tones, an output system coupled to receive the signal. from the generating means upon operationof the playing keys, a switch for each of` the keys, a plurality of cascaded electron discharge devices, each of said devices being normally biased beyond cutoff, means controlled by the key switches to render the first of said devices conductive, a relay operable by the first of the devices to remove the biasing potential from the following devices of this series, meansy operable by the relay of the rst device to connect a source of operating potential to the second device of the cascaded series, means for introducing a predetermined time delay in renderingthe second device effective, means controlled by the second of said devices and each subsequent device except the last of the cascaded series operable to render the succeeding device conductive after a predetermined time interval, and a relay energized by each of said devices and operable to change the effectiveness of the coupling between thev tone signal generating means and the output system, thereby to cause the tone intensity envelope to have a predetermined intensity envelope.

1 9. In an electrical musical instrument having an electrical tone signal generating system, an output system, and playing key operated means for controlling the transmission to the output system of the electrical tone signals produced by the generating system, the combination of a switch associated with each playing key for operation thereby, a plurality of tone signal attenuating means forming part of the output system, means for changing the effectiveness of the attenuating means at a predetermined rate, an electromagnetic device for operating said lastnamed means at a predetermined rate, and a plurality of parallel circuits for initiating energizationV of said device, each of said circuits including a source of energy, said device, and one of 'the switches in series,

JOHN M. HANERT.

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

UNITED STATES PATENTS Number Name Date 2,161,706 Hammond June 6, 1939 2,270,789 Smith Jan. 20, 1942 2,301,871 Hanert Nov. l0, 1942 FOREIGN PATENTS Number Country Date 838,670 France Dee. 16, 1938

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