US 3250843 A
Description (OCR text may contain errors)
May 10, 1966 JENNY 3,250,843
ELECTRONIC MUSICAL INSTRUMENT WITH FLUID PRESSURE ACTUATED VOLUME CONTROL Filed Aug. 19, 1964 3 Sheets-Sheet l Filfer|-1 Oscillafion Generator Georges Jenny IN V EN TOR.
AGENT May 10, 1966 G. JENNY 3,250,843
ELECTRONIC MUSICAL INSTRUMENT WITH FLUID PRESSURE AGTUATED VOLUME CONTROL Filed Aug. L9, 1964 C5 Sheets-Sheet 2 A A A L 3 i 48 ,4 HI Variable Resisfance /9 7 a o I 50 I I f H is I Y l 2 I \V I 4 I Georges Jenny IN V EN TOR.
' AGENT May 10, 1966 e. JENNY 3,250,843
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OSCil/ On .7 fiefl df V r v Q frolyfmlmpregnmed per I d Gear 35 Jenn F0 9- 5 2 I lNp- To By W9 United States Patent 3,250,843 ELECTRONIC MUSICAL INSTRUMENT WITH FLUID PRESSURE ACTUATED VOLUME CONTROL Georges Jenny, Quessigny (Euro), France Filed Aug. 19, 1964, Ser. No. 390,694 8 Claims. (Cl. 841.09)
This application is a continuation-in-part of my application Ser. No. 123,818, filed July 13, 1961.
My present invention relates to a musical instrument of the type wherein notes of dilferent audible 'frequencies are produced with the aid of an electronic oscillation generator under the control of individually operable tone selectors, such as a set of buttons or keys of a key board.
Although the operation and control of such electronic tone generators is well known per se, it has not yet been possible to operate them in such a way that their acoustic performance resembles that of conventional body-operated musical instruments, particularly wind instruments.
Thus, notes produced by wind instruments (a term here intended to include. not only instruments actuated by the mouth of the player, such as flutes, harmonicas and the like, but also instruments such as accordions in which the wind is generatedby manual compression and expansion of a bellows) have a distinct intensity characteristic which is due to the fact that the medium which excites the individual sound generators, e.g. reeds, is an intermittent air stream which varies in intensity, and sometimes (as in a harmonica or accordion) in direction, at a subaudible rate so that there occurs a distinct amplitude modulation of each note. The general object of my invention is to provide, in an electronic musical instrument, means for simulating the performance of such wind instruments,
This object is realized, in accordance with my present invention, by the provision of a body-actuated source of air flow, such as a mouthpiece or a bellows operable by hand or foot, in combination with flow-backing means oscillat-able at subaudible frequencies or otherwise displaceable at a relatively slow rate in response to variations o-r reversals of the air flow, the flow-blocking means electrically controlling an amplitude-modulating network in the output circuit of an associated electronic tone generator.
The flowblocking means, positioned, to intercept the air current from the mouthpiece or bellows, may be a closed or substantially closed elastic bag, a spring loaded piston, or some other element resiliently obstructing or impeding the flow. Resilient biasing, however, is not absolutely essential in the case of a reversible air flow, e.g. as produced by an accordion, in which, for example, an elastic or inelastic membrane may be used as the flowblocking and pressure-responsive element. Such a membrane, which can be regarded as a double-acting piston, may also be replaced by a pair of oppositely biased pistons disposed side by side and interconnected by a mechanical linkage which in turn acts upon a variable impedance element constituting part of the amplitude-modulating network. This network may also include other selectively adjustable impedances, e.g. capacitors, for varying its time constant and therefore the response characteristics of the modulator. Mechanical variation of this response characteristic is possible, alternatively or supplementally, with the aid of devices for selectively throttling the flow of air into or past the flow-blocking means.
The amplitude of the generator may also be modulated more directly by passing its oscillating output current through a potentiometer or other variable impedance element controlled by a device which responds to the pressure of the air flow. I have found, in accordance 3,250,843 Patented May 10, 1966 "ice with a further feature of my invention, that a particularly suitable potentiometer for this purpose comprises a wiper with a porous body permeated by an electrolytic liquid so that the resistance element of the potentiometer is contacted by liquid film rather than by a solid conductor, with the result that friction and backlash are minimized. A very effective electrolytic liquid for this purpose is a solution of magnesium chloride in a nonvolatile alcohol, preferably glycerol. I
The above and other features of my invention will become more readily apparent in the following detailed description of certain embodiments, reference being made to the accompanying drawing in which:
FIG. 1 is a partly diagrammatical view of a mouthoperated modulating system according to the invention, as originally disclosed in my above-mentioned copending application;
FIG. 2 is a cross-sectional view of an accordion embodying the invention in modified form;
FIG. 3 illustrates, again partly diagrammatically, a further modification of the invention as applied to an accordion;
FIG. 4, in still another partly diagrammatical view, illustrates a further embodiment; and
FIG. 5 diagrammatically shows yet another embodiment.
In FIG. 1 I have illustrated a keyboard whose keys 11 individually control, in a manner known per so, an oscillation generator 12 via a Set of conductors symbolized by a connection 13. An output lead 14 of generator 12 terminates at the control grid of an amplifier tube 15, here shown as a tetrode, whose plate is connected to a high positive voltage via a resistor 16 and is further coupled to a loudspeaker 17 by way of a blocking condenser 18 and a filter 19. The screen grid of tetrode is connected via leads 33, 34 to positive voltage at a battery 20 by way of a set of variable resistances 21, 22, 23 all connected in parallel, these resistances consisting for example of blocks of electrically conductive foam rubber whose conductivity increases as the blocks are compressed. A metal plate 24, pivotally mounted at 25, bears upon the blocks 21-23 under pressure of an inflatable bag 26 of resilient material, e.g. rubber, having a mouthpiece 27 into which the user mayblow. A shunt circuit of manually adjustable impedance, including a first condenser 28 in series with a switch 29 and a second condenser 30 in parallel therewith, is connected across the variable-impedance unit 21-27 to permit selective altering of the time constant of the RC network 20-30 connected to the screen grid of amplifier tube 15.
In operation, a skilled musician will be able to produce a variety of artistic expressions in modulating the output of tone generator 12, as selected with the aid of keyboard 10, under the control of his own breath as he blows more lightly or more strongly into the mouthpiece 27; in the absence of any air pressure applied to the bag 26, the conductive plate 24 may be disconnected from the resistances 21-23 so that the screen grid of tube 15 receives negative bias from a battery 31 through a large resistance 32 and the tube 15 is elfectively cut off. Naturally, the resistances 21-23 may also be so arranged that the tube 15 retains some conductivity in the no-pressure condition whereby a note of minimum intensity can be heard when one of the keys 11 is depressed without concurrent blowing.
In FIG. 2, I have shown at the bellows of an otherwise conventional accordion provided with an attachment 41 which forms a passage 42 communicating with the interior of the bellows. Passage 42 has a pair of lateral ports 43, 44 in which two pistons 45, 46 are movable in response to pressure differentials between the interior of the bellows and the surrounding atmosphere; piston 45 is displaceable when this pressure differential is positive, i.e. when the bellows 40 is compressed whereas piston 46 leaves its normal position when suction is created by an extension of the bellows. The keyboard of the accordion (not shown) is connected, in the manner illustrated for keyboard of FIG. 1, to an oscillation generator whose output is amplitude-modulated by an amplifier such as the tube of FIG. 1, having an input lead 33, connected to a conductive bracket 47 carrying a block 48 of variable electrical resistance similar to the blocks 21-23 of FIG. 1. The rods 45', 46' of pistons 45 and 46 bear upon opposite extremities of a lever 49 whose center is fulcrumed to a bar 50 depending from a conductive plate 51 which in turn is connected to the conductor 34 leading to a source of bias voltage as shown in FIG. 1.
It will be apparent that the differential linkage 45', 46, 49-51 in the system of FIG. 2 applies pressure to the variable resistance 48 upon both compression and expansion of the accordion bellows 40, thereby modulating the amplitude of the notes produced by the associated tone generator. This instrument, therefore, can be worked essentially in the same manner as the one shown in FIG. 1, except that the air pressure is now applied manually rather than by mouth. Naturally, the performance of the tone generator may be further controlled by adjustable impedances, e.g. as illustrated at 2830 in FIG. 1.
In FIG. 3, I have shown an accordion bellows 60 having a flexible membrane 61 inserted in an end wall thereof. Membrane 61-is conductively coated and electrically connected to a source 62 of alternating current whose other terminal is connected to a pair of rigid plates 63, 64, spaced from the membrane on opposite sides thereof, via the primary windings of respective transformers 65, 66. The secondary windings of these transformers are connected to the grids of a pair of triodes 67, 68 connected in push-pull across a source of operating voltage here shown as a battery 69, the two grids being biased by another battery 70; tubes 67 and 68 work into an output transformer 71 connected to a detector 72 which applies their rectified output to the lead 33 of the amplitude modulator (not shown in this figure).
In operation, deflection of the membrane 61 in either direction by the operation of bellows 60 will unbalance the push-pull in connected tubes 67, 68 by making the capacitance of one input condenser 61, 63 different from that of the other input condenser 61, 64 so that a control voltage will appear on the lead 33 in the output of detector 72. The magnitude of this control voltage will again be determined by the pressure differential existing between the interior of the bellows and the surrounding atmosphere but will be substantially independent of the sign of this differential. The bias of battery 70 may also be made sufliciently negative to cut off both tubes 67, 68 until the deflection of membrane 61 is substantial enough to lower the impedance of either condenser 61, 63, or 61, 64 to less than a predetermined cutoff value whereby only one or the other of the tubes 67 and 68 will conduct at any time.
In FIG. 4, I have shown an inlet tube 80 through which a flow of air, originating for example from a mouthpiece as shown at 27 in FIG. 1, enters an enclosure 81 provided with an internal partition 82. On one side of this partition there is disposed a light source 83 whose rays are directed toward a photoelectric cell 84 on the opposite side of the partition, the path of the rays being normally cut off by a light gate represented by a swingable baflle 85 which is urged under pressure of a spring 86 against the partition 82. The oncoming air stream opens the light gate to a greater or lesser extent, depending on its intensity, by deflecting the baffle 85 against the force of its biasing spring 86 so that the air may escape through an outlet 87; this outlet carries a throttle valve 88 for regulating the flow resistance of the passage 80, 81, 87.
Light source 83 is a glow tube energizable by :a battery 89 via a pair of normally open contacts 90 which are closed upon depression of any key 11 of the keyboard 10 4 (see FIG. 1), the contacts of all the keys 11 being connected in parallel. FIG. 4 also illustrates another set of contacts 91 individual to the particular key 11, which connect ground potential to the associated conductor 13 leading to the oscillation generator. Photocell 84 is energized by a battery 92 and has its output electrically connected to the control lead 33 of the amplitude modulator.
In operation, battery 92 applies a control voltage to lead 33 only upon illumination of photocell 84 when the light gate 85 is partly or fully opened, the magnitude of this voltage thus depending upon the intensity of the air stream flowing through tube 80 and exiting via outlet 87. This air stream is again under direct body control of the operator, Whether produced by blowing, manual compression of a bellows or stepping upon a pedal, so that the acoustic output of the tone generator will reflect the artistic performance of the operator.
In FIG. 5, finally, there is illustrated a potentiometer connected in the output lead 14 of the oscillation generator 12, this potentiometer including a resistance 101 contacted by a wiper 102 on the free end of a conductive spring 103 which in turn is connected to the loudspeaker 17. Spring 103 is acted upon by the bag 26 of FIG. 1 so as to make the wiper 102 slide along the resistance element 101 as the bag is inflated by blowing into'the mouthpiece 27. Wiper 102 has a porous body e.g. of felt, permeated by a conductive liquid, preferably a source of magnesium chloride in glycerol; a proportion of three parts glycerol (by volume) to one part of MgCl has been found extremely suitable. It should be noted that this solution, like any other electrolyte, would tend to polarize it direct current were applied to the potentiometer; with the arrangement illustrated, in which the alternating output of oscillator 12 passes through the potentiometer, this is not the case.
The potentiometer 100 shown in FIG. 5 operates substantially without inertia and quickly responds to the expansions and contractions of the bag 26 at subaudible frequencies. Naturally, a potentiometer of this kind could also be used with, for example, a piston type controller of the construction shown in FIG. 2 or other control device responsive to air pressure. Other compatible features shown in dilferent embodiments may be similarly combined, these and further modifications readily apparent to persons skilled in the art being intended to be embraced within the spirit and scope of my invention as defined in the appended claims.
1. In a musical instrument having an electronic tone generator provided with a control circuit, electro-acoustic transducer means connected to the output of said generator, and a multiplicity of individually operable tone selectors connected to said generator for energizing the latter to produce electrical oscillations with a variety of audible frequencies translatable by said transducer means into sound waves, the combination therewith of a bodyactuated source of air flow, flow-blocking means displaceable in response to variations of said air flow, and ampli tilde-modulating means for said oscillations controlled by said flow-blocking means, said amplitude-modulating means including a pressure-sensitive impedance element of compressible resistance material connected in said control circuit and a physical connection from said flow-blocking means to said element.
2. The combination defined in claim 1 wherein said source comprises a mouthpiece.
3. The combination defined in claim 1 wherein said source comprises a manually operable bellows.
4. The combination defined in claim 2 wherein said flow-blocking means comprises an inflatable bag.
5. In a musical instrument having an electronic tone generator provided with a control circuit, electro-acoustic transducer means connected to the output of said generator, and a multiplicity of individually operable tone selectors connected to said generator for energizing the latter to produce electrical oscillations with a variety of audible frequencies translatable by said transducer means into sound waves, the combination therewith of a bodyactuated source of reversible air flow, means forming a pair of interconnected passages for said air flow, first and second flow-blocking means respectively displaceable in said passages in response to air flow in either of two directions, and amplitude-modulating means for said oscillations controlled by said first and second flow-blocking means, said amplitude modulating means including a variable impedance element connected in said control circuit and a physical connection from each of said flow-blocking means to said element.
6. The combination defined in claim 5 wherein said physical connection comprises a differential linkage.
7. The combination defined in claim 5 wherein said impedance element comprises a pressure-sensitive body of compressible resistance material.
8. In a musical instrument having an electronic tone generator provided with a control circuit, electro-acoustic transducer means connected to the output circuit of said generator, and a multiplicity of individually operable tone selectors connected to said generator for energizing the latter to produce electrical oscillations with a variety of 10 lating means comprising variable impedance means connected in said output circuit and physically coupled with said linkage.
References Cited by the Examiner 15 UNITED STATES PATENTS 1,975,220 10/1934 Ananiew 841.27 2,301,184 11/1942 Arnold 841.27 X 2,475,168 7/1949 Workman 841.01
2Q FOREIGN PATENTS 424,892 2/ 1935 Great Britain.
4 GEORGE N. WESTBY, Primary Examiner.