US3704339A

US3704339A - Muscular voltage-controlled tone-modifying device

Info

Publication number: US3704339A
Application number: US115981A
Authority: US
Inventors: Naoyuki Niinomi
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1971-02-17
Filing date: 1971-02-17
Publication date: 1972-11-28
Anticipated expiration: 1989-11-28

Abstract

An electronic musical instrument is controlled also by the muscular voltage of the instrument player. A pair of electrodes are mounted on any selected portion of the skin of the player in order to pick up a muscular voltage appearing across a muscle upon a contraction thereof. The picked-up voltage is amplified and processed into a control signal which in turn controls the tone signal modifying circuit in the instrument. While the player is engaged in the ordinary performance using hands and feet, further effect control can be carried out at the player''s will.

Description

United States Paten Niinomi [72] Inventor: Naoyuki Niinomi,

Japan [73] Assignee: Nippon Seizo' Kabushiki Kaisha, Hamatnatsu-shi, Shizuokaken, Japan [22] Filed: Feb. 17, 1971 [21] Appl.N0.: 115,981

[30] Foreign Application Priority Data Feb. 18, 1970 Japan ..45/ 14049 Feb. 23, 1970 Japan ..45/l7670 Feb. 23, 1970 Japan ..45/l767l Feb. 26, 1970 Japan ..45/l9l2O Feb. 26, 1970 Japan 45/19121 May 16, 1970 Japan ..45/47923 May 16, 1970 Japan ..45/47924 May 16, 1970 Japan ..45/47925 May 16, 1970 Japan ..45/47926 I May 22, 1970 Japan ..45/50227 May 22, 1970 Japan .....45/50228 52 us. c1. ..s4/1.24, 84/112, 84/l.13,

84/126, 84/127 [51] Int. Cl. ..Gl0h l/02 MUSCULAR VOLTAGE-CONTROLLED TONE-MODIFYING DEVICE Hamamatsu,

3,704,339 Nov. 28, 1972 [58] field of Search....3/1.l; 128/2106; 84/1.01, 1.24

[56] Met-6666s c1166 UNITED STATES PATENTS 3,426,150 2/1969 Tygart ..128/2.06 x 2,712,975 7/1955 06186111 et a1 ..128/2.06 x 3,199,508 8/1965 Roth ..128/2.o6 3,565,058 2/1971 Mansfield ..128/2.o6

Primary Examiner-Lewis H. Myers Assistant ExaminerU. Weldon Attorney-Cushman, Darby & Cushman 57 9 ABSTRACT An electronic musical instrument is controlled also by I the muscular voltage of the instrument player. A pair 28 Clains, 47 Drawing Figures INVENTOR.

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MUSCULAR VOLTAGE-CONTROLLED TONE- MODIFYING DEVICE BACKGROUND OF THE INVENTION The present invention generally relates to an electronic musical instrument having a novel control system, and more particularly, it relates to an electronic musical instrumenthaving a muscular voltagecontrolled tone modifying circuit. g

In the conventional electronic musical instrument,

many of them have been primarily designed so as to be BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an illustration representing an electronic musical instrument having a muscular voltage-controlled tone modifying circuit according to an embodiment of the present invention;

FIG. 2 is a schematic circuit block-diagram showing an example of a muscular voltage-controlled circuit system;

FIGS. 3A and 3B are illustrations representing the muscular system as viewed from front and back of man;

FIG. 4 is a block diagramshowing the essential portion of a muscular voltage processing circuit;

FIG. 5 is a block diagram showing another example of FIG. 4;

FIGS. 6A through 6B are waveforms used primarily for explainingthe operation of the circuit shown in such as piano, guitar and the like. Hence, the will of the player could not be satisfactorily reflected. Furthermore, the operation of the instruments could not be controlledwithout the application of motion of the players hands and feet to the mechanical switches associated with several tone modifying circuits of the instruments. Thus, the conventional tone modifyingcircuit control system has required very troublesome manual operation by the player and has been quite in convenient in actual playing. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide an electronic musical instrument in which muscular voltages generated upon contraction of-a muscle of the player are used as control signals for several tone modifying circuits of the instrument to enhance expression or variety of tonal effects of music being played. I I

Another object of thepresent invention is to provide an electronic musical instrument which requires no manual actuation of expression pedals or stop tablets,

by the provision of muscular voltage-actuated controls electrically connected with pickup electrodes mounted on any selected portion of the skin surface of the player.

A further object of the present invention is to provide an electronic musical instrument provided with muscular voltage pickup means capable of picking up, with a high efficiency, a minimal muscular voltage caused by the motion or stiffening of desired portions of muscles of the player.

A still further object of the present invention is to facilitates interconnection between several tone-modifying circuits of the instrument and muscular voltage pickup means mounted on various desired physical portions of the player and having muscular voltage Other objects, features and advantages of the present invention will become apparent from the following the accompanying drawings.

provide an electronic musical instrument which.

FIG. 5;

FIGS. 7A to 7C are illustrations representing the interconnection between a console of an electronic musical instrument and a muscular voltage pickup means;

FIGS. 7D and 7E are diagrams showing examples of connection'be tween the console of the instrument and a lead from the pickup means;

FIG. 8 is an illustration representing another example of muscular voltage pickup means and the associated circuits; 1

FIGS. 9A and 9B are illustrations representing another example of the interconnection shown in FIG.

FIGS. 10A to 10D are views showing several aspects of the muscular voltage pickup means, respectively;

FIGS. 11A to 11F, FIGS. 12A to 121 and FIGS. 13A to 13G are views showing various kinds of mounting means for the muscular voltage pickup means; and I FIGS. 14A and 14B areiviews showing shielding wear provided with the muscular voltage pickup means.

It is to be understood that like references and numerals indicate like parts.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is illustrated an electronic musical. instrument such as a key-actuated electronic organ generally indicated at l which comprises as its playing

actuatorsmanual keyboards

2 and 3 arranged in multiple stages, a pedal keyboard 4, an expression pedal 5, etc. A pair of

electrodes

6a and 6b electrically associated with a grounded electrode are adapted to be securely mounted on the body of the player at appropriate positions of an arm 6 of the player, for example, on the skin surface on the inside of the forearm, by

means of an electrically conductive paste or an electrically conductive bonding tape, so that a muscular voltage produced upon contraction of a muscle of the arm and appearing at the skin on which the electrodes are mounted may be picked up.

The

electrodes

6a and 6b are also connected with both ends of a primary winding L of a transformer L, while the secondary winding I thereof is connected to an input side of an amplifier circuit A; of which the output is connected through a rectifier circuit D to a terminal t.

Thus, the block E constitutes a muscular voltage processing circuit including said transformer L, said amplifier A said rectifier D and the terminal t. The picked-up muscular voltage which is generated upon contraction of the electrode-loaded muscle is amplified and rectified, thus developing a DC output signal depending on the muscular voltage at the terminal t.

Referring now to FIG. 2, there is shown an embodiment of muscular voltage-controlled tone modifying circuits (see, e.g., Journal of the Audio Engineering Society, vol. 13, No. 3, July, 1965, pages 200-206) such as a vibrato effect imparting circuit, atone coloring circuit and a tremolo effect imparting circuit of the instrument which are adapted to receive at its input the DC output signal developed at the output of the circuit E as a control signal, whereby either a tone signal in the instrument or the control circuit for controlling a tone signal-modifying circuit is subjected to the control by its electrical characteristics such as amplitude, frequency and phase to thereby vary the tone volume, the tone pitch, the tone color or other tonal effects in the instrument.

Symbol 0 represents tone source circuits which correspond in number to that of keys-arranged in the instrument. Individual tone signals generated by a number of said tonesource circuits are keyed by respective key-operated keying circuits: K and then the keyed tone signals are entered to tone coloring circuits F having filters therein. The output signals of the tone coloring circuits are applied to an amplifier circuit A and therefrom to the electro-acoustic transducer such as a speaker S.,To the tone source circuits 0 is also connected a vibrato effect-producing circuit V, i.e., a very low frequency oscillator, whereby individual oscillation frequencies at the oscillators of the tone source circuits 0 are varied to provide vibrato effects. Between the tone coloring circuits and the amplifier circuit A are provided tremolo effect producing circuit M which effects amplitude modulation of the input tone signals to produce tremolo effects. Thus, a circuit G including the above-mentioned circuits constitutes a conventional electronic musical instrument circuit. However, to the respective control terminals of these tone signal modifying circuits are connected output terminals of corresponding muscular voltage processing circuits E E E, which are similar to that E shown in FIG. 1, of which the inputs may be provided from muscular voltage pickup means mounted on biceps 6 extensor digitiformcommunis 6,, trapezius 7, sternocleidomastoid 8, vastus lateralis and vastus medials 9, and biceps of the thigh 9, in the muscular system of man, as shown in FIGS. 3A and 3B, in the same manner as that described in connection with FIG. 1.

DC signals at terminals t t t,,, whose levels depend on the magnitude of the picked-up muscular voltages, i.e., the amount of contraction of the above-mentioned muscles, act to vary the oscillation frequency or oscillation output level of the vibrato effect-producing circuit V, to vary the frequency characteristic of the filter in each tone coloring circuit F and also to vary the degree of amplification of the amplifier circuit A, respectively. For example, the muscular voltage processing circuit E, may be arranged to receive a muscular voltage which is picked up by the .muscular' voltage pickup means, i.e., electrodes, which are mounted on the biceps 6 or the extensor digitiform communis 6 upon extension or bending of the arm or the fingers, as a waveform shown in FIG. 6A, and to amplify and rectify it to produce a pulsating DC waveform shown in FIG. 6D whose levels depend on the degree of contraction of the

muscles

6, and 6 while the amplifier A may be arranged to have a variable impedance element such as a gate-controlled field effect transistor for variably controlling its output level so as to vary the output volume of the speaker S in accordance with the degree of said extension or bending of muscle by application of said pulsating DC voltage to the gate of the transistor. Accordingly, the impedance of the variable impedance element can be increased or decreased in accordance with the degree of contraction of muscle, and hence, the same effect as that produced by the conventional expressionpedal .type instrument may be obtained, for example, by bending the arm or fingers having pickup meansmounted thereon or by applying a force thereto. Instead, the pickup means may be mounted on the trapezius 7 or the bicepsof a thigh 9 to pick up the muscular voltages, where the output volume of the instrument may be adjusted by an up and down motion of the shoulder or the leg. The greater the amount of contraction of muscle or the force applied thereto is, the greater will be the magnitude of the muscular voltage generated, whereas the smaller the amount of contraction or force is, the less will be the magnitude of the muscular voltage produced. Thus, the muscular voltage generally may be said to increase or decrease in accordance with the magnitude of extension or bending of arm or fingers. The muscular voltage, however, can be increased or decreased only by applying a force to the muscle.

Each of the tremolo effect producing circuit M, the vibrato effect producing circuit V and the tone coloring circuit F can be controlled also analogously by the use of muscular voltage generated depending on the degree of contraction of muscles in such a manner as has been described in connection with the control of the amplifier A.

The oscillation frequency at the tremolo frequency oscillator'circuit or the vibrato oscillator circuit may be changed accordance with'the degree of the muscular contraction, by varying the resistance component of a bias circuit or a CR coupling circuit which is used in said oscillator circuit using the above-mentioned variable impedance element.

As shown in FIG. 4, an electromagnetically actuated stop tablet J of the instrument may be controlled by a square pulse signal shown in FIG. 6B at the output of a monostable multivibrator H to the input of which the output signal of the muscular voltage processing circuit E, (E E,,) is supplied, without manipulation thereof. Thus, the control operation for obtaining a variety of effects in the instrument is greatly facilitated.

Referring now to FIG. 5', there is shown a modification of each of the muscular voltage processing circuits E,, E E,,, in which, for noise rejection, a non-linear circuit 11 (see, e.g., Reich, Functional Circuits and Oscillators, 1961, pages 297-306 and a bandpass filter 12 are series-connected between the amplifier A, and rectifier circuit 13. Thus, thecircuits l1 and 12 can serve to reject electromagnetically or electrostatically induced noise component which is contained in the picked-up muscular voltage as shown in FIG. 6A,

developing a waveform as shown in FIG. 6B. Such a waveform is passed through the rectifier 13 into the waveform of FIG. 6C.

Now, the muscular voltage thus derived, of course,is applicable to various controls of other musical instruments, e.g., an electric guitar or an electric piano, and to the control of devicesprovided in electric or electronic musical instruments.

Referring to FIG. 7A, there is-shownan illustration of an interconnection between an electronic organ console 21 and a muscular voltage pickup means by way of example, in which numerals 22 and 23 represent manual keyboards, numeral 24 a pedal keyboard.

Numerals

26, 30 and 31 represent an arm, a trapezius, and biceps of a thigh of the player, respectively, on each of which is mounted a pair of electrodes constituting a muscular voltage pickup means, for example as shown by

numerals

27a and 27b.

Numerals

28, 32 and 33 are shielded lead wires for introducing muscular voltages from the pickup means into tone signal modifying circuits of the instrument, which lead wires are detachably couplable on the instrument console through connector plug assembly. That is to say, at one of each lead wire is provided an insertion plug 29, 34 or 35, while ganged receptacles or jacks therefor, J I and J are mounted in position on a front plate 21A of the console. Alternatively, female snap members 38a and: 38!; may be mounted on the front plate 21A in place of the receptacles J J and J and male snap member 39 having

circular parts

39a and 39b may be substituted for the plugs 29, as shown in FIGS. 7B and 7C. At the hot side of each receptacle is connected a shielded

wire

36a, 36b or 360. These shielded wires which are 'capable of transmitting the picked-up muscular voltages are connected to stationary contacts 8,, S, and S, of onepole three positions type changeover switch S positioned at an upper portion of the front plate of the console, the movable contact of which may be connected to a muscular voltage processing circuit E as shown in FIG. 7D. Alternatively, one or all the hot sides of the receptacles may be connected to the movable contact of the switch S with the stationary contacts being connected to respective muscular voltage processing circuits E E and E through shielded

wires

37a, 37b and 370, as shown in FIG. 7E.

FIG. 8 shows another example of the muscular voltage transmission route similar to that shown in FIG. 7A. In this example, however, the shielded wire comprises paired conductors incorporated therein.

FIG. 9A shows a modification of FIG. 7A, in which a junction box is provided in a chair for the player to connect the outputs of muscular voltage pickup means to muscular voltage processing circuits housed in the console of the instrument. The one-pole three positions type changeover switch S may also be housed in the chair instead of the console, as shown by S Alternatively, the muscular voltage processing circuits may also be housed in the junction box.

In FIG. 98, there is illustrated a manner in which an external lead wire is detachably secured to the junction box.

FIGS. A to 108 show several examples of the muscular voltage pickup means of the present invention, in which numerals 76a and 76b represent a pair of electrodes, numeral 81 lead conductors, numeral 77 an adhesive mount formed of a cloth or a plastic film and provided with said paired electrodes with a suitable distance left therebetween. Numerals 78a and 78b represent openings, numeral 79 a snap terminal plate,

5 numeral 83 a shielding material such as a metallized 10 voltage pickup means utilizing

gloves

97a and 97b for mounting

pickup electrodes

96a and 96b, in which numerals 99a to 99e represent lead wires connected to said electrodes. In FIG. ll'C, a shielding means 100 is grounded through lead 101 for noise prevention.

FIG. 11D shows an example of the detachable pickup means in which leads 103a and l03b are detachably connected to

external leads

102a and 102b by means of a snap terminal 104. FIGS. 11E and 11F show examples of

boots

105 and 106 mounted with said

electrodes

96a and 96b.

FIGS. 12A to 12I show various kinds of wears on which muscular voltage pickup electrodes 116a and 1 16b may be loaded.

FIGS. 13A to 13G show various examples of personal accessories such as a finger ring, a spectacle frame, a wrist watch band, etc. on which muscular

voltage pickup electrodes

136a and 136b may be mounted. FIG. 14A shows essential portions of a shielding cloth which is made of a conductive fiber cloth 159 woven with conductive fibers 157 and non-conductive fibers 158, both fibers constituting woofs and warps as desired. A snap terminal 160 is attached to said conductive cloth, and detachably engages a member hav- 3 5 ing grounded conductor 161 therein.

FIG. 148 shows another example of a shielding clothe 162, which includes a conductive cloth 164 having a thin metal film deposited thereon or metal powder sprayed thereon.

I claim: 1. A muscular voltage-controlled tone-modifying device in an electronic musical instrument comprising:

at least one pair of electrodes adapted for mounting I on a human body adjacent a muscle of the human body for detecting a muscular voltage which is produced upon contraction of said muscle,

a pair of lead conductors connected to said electrodes,

at least one muscular voltage processing circuit including amplifying means connected through said lead conductors to said electrodes for receiving and amplifying said detected voltage, to produce an output voltage signal,

tone signal modifying circuits having control terminals, and

means for applying said output voltage signal derived from said processing circuit to said control terminals of said tone signal modifying circuits, so that said tone signal modifying circuits are controlled in response to an intended motion of the muscle to which the electrodes are attached.

2. A muscular voltage-controlled tone-modifying device according to claim 1, further comprising:

65 at least one connector provided on a casing of the in- 3. A muscular voltage-controlled tone-modifying device according to claim 1, in which said processing circuit includes rectifying means provided between said amplifying means and said tone signal modifying circuits for developing a DC signal from the amplified muscular voltage. I 1

4. A muscular voltage-controlled tone-modifying device according to claim 1, in which a connector assembly is providedin a chair for the player of the instrument to detachably connect the lead conductors from said pickup electrodes to said processing circuit.

5. A muscular voltage-controlled tone-modifying device according to claim 4, in which said processing circuit is provided in said chair.

6. A muscular voltage-controlled tone-modifying device accordingtto, claim 1, in which said one pair of pickup electrodes are associated through a switching means. with a plurality of said muscular voltage processing circuits of which each is connected to a different musical effect producing circuit to be controlled so as to obtain an intended effect.

7. A muscular voltage-controlled tone-modifying device according to claim 1 in which a plurality of said paired electrodes are provided for difierent muscles of the players body individually, each pair being associated with said muscular voltage processing circuit through a switching means. i

8. A muscular voltage-controlled tone-modifying device according to claim 1, in which said muscular voltage processing circuit includes an amplifier for amplifying a picked-up muscular voltage, a non-linear circuit for receiving an amplified voltage from said amplificr and cutting noise component contained in this voltage, a bandpass filter connected to the output of said non-linear circuit, and a rectifier receiving and rectifying the picked-up voltage passing through the bandpass filter to provide a unidirectional voltage.

9. An electronic musical instrument comprising a plurality of audio tone producing circuits,

means for causing, when manually operated, said tone producing circuits to produce said tones, means for connecting said producing circuits to said causing means,

electrode means for detecting the muscular voltage produced by at least one muscle on a human body, means for varying an audio characteristic of the tones produced by at least one of said circuits as a function of said detected muscular voltage and means for connecting said varying means to said electrode means and to said producing circuits.

10. 'An instrument as in claim 9 including means for amplifying said detected muscular voltage to produce a control signal.

1 1. An instrument as in claim 10 including means for rectifying the amplified voltage to produce said control signal.

12. An instrument as in claim 9 wherein said varying means includes means for varying the amplitude of said I tones as a function of said muscular voltage.

13. An instrument as in claim 9 wherein said varying means includes means for varying the color of said tones as a function of said muscular voltage.

, 8 l4. An instrument as in 9 wherein said varying means includes the means for imparting a tremolo effeet as a function of said muscular voltage,

15. An instrument as in claim 9 including means for mounting a pair of electrodes on the exterior of the human body adjacent said muscle.

16. An instrument as in claim 15 including means for mounting a plurality of pairs of electrodes on the exterior of the human body each adjacent a muscle for each detecting the muscular voltage of the muscle which it is adjacent.

17. An instrument as in claim 9 including means for mounting a pair of electrodes on an article of clothing.

18. An instrument as in claim 9 wherein said causing means includes a plurality of keys each operatively connected to one of said-tone producing circuits.

19. A method of operating an electronic musical instrument of the type having a plurality of audio tone producing circuits and means for manually operating said circuits tofproduce audio tones comprising the steps of:

manually operating said tone producing circuits to produce said tones,

detecting the muscular voltage produced by at least one muscle on a human body, generating a control signal from said muscular voltage,

applying said control signal to said tone producing circuits, and

varying an audio characteristic of the tones produced by at least one of said circuits as a function of said control signal. i

20. A method as in claim 19 including the further step of amplifying said detected muscular voltage to produce a control signal.

21. A method as in claim 20 including the further step of rectifying the amplified voltage to produce said control signal.

22. A method as in claim 19 wherein said step of varying includes the step of varying the amplitude of said tones as a function of said muscular voltage.

23. A method as in claim 19 wherein said step of varying includes the step of varying the color of said tones as a function of said muscular voltage.

24. A method as in claim 19 wherein said step of varying includes the step of imparting atremolo effect as a function of said muscular voltage.

25. A method as in claim 19 including the step of mounting a pair of electrodes on the exterior of the human body adjacent said muscle.

26. A method as in claim 25 including the step of mounting a plurality of pairs of electrodes on the exterior of the human body each adjacent a muscle for each detecting the muscular voltage of the muscle which it is adjacent.

27. A method as in claim 19 including the step of mounting a pair of electrodes on an article of clothing.

28. A method as in claim 19 wherein said step of manually operating includes manual depression of keys each operatively connected to one of said tone producing circuits.

Claims

1. A muscular voltage-controlled tone-modifying device in an electronic musical instrument comprising: at least one pair of electrodes adapted for mounting on a human body adjacent a muscle of the human body for detecting a muscular voltage which is produced upon contraction of said muscle, a pair of lead conductors connected to said electrodes, at least one muscular voltage processing circuit including amplifying means connected through said lead conductors to said electrodes for receiving and amplifying said detected voltage, to produce an output voltage signal, tone signal modifying circuits having control terminals, and means for applying said output voltage signal derived from said processing circuit to said control terminals of said tone signal modifying circuits, so that said tone signal modifying circuits are controlled in response to an intended motion of the muscle to which the electrodes are attached.

2. A muscular voltage-controlled tone-modifying device according to claim 1, further comprising: at least one connector provided on a casing of the instrument for detachably connecting the lead conductors to said processing circuit and said tone signal modifying circuits.

3. A muscular voltage-controlled tone-modifying device according to claim 1, in which said processing circuit includes rectifying means provided between said amplifying means and said tone signal modifying circuits for developing a DC signal from the amplified muscular voltage.

4. A muscular voltage-controlled tone-modifying device according to claim 1, in which a connector assembly is provided in a chair for the player of the instrument to detachably connect the lead conductors from said pickup electrodes to said processing circuit.

6. A muscular voltage-controlled tone-modifying device according to claim 1, in which said one pair of pickup electrodes are associated through a switching means with a plurality of said muscular voltage processing circuits of which each is connected to a different musical effect producing circuit to be controlled so as to obtain an intended effect.

7. A muscular voltage-controlled tone-modifying device according to claim 1 in which a plurality of said paired electrodes are provided for different muscles of the player''s body individually, each pair being associated with said muscular voltage processing circuit through a switching means.

8. A muscular voltage-controlled tone-modifying device according to claim 1, in which said muscular voltage processing circuit includes an amplifier for amplifying a picked-up muscular voltage, a non-linear circuit for receiving an amplified voltage from said amplifier and cutting noise component contained in this voltage, a bandpass filter connected to the output of said non-linear circuit, and a rectifier receiving and rectifying the picked-up voltage passing through the bandpass filter to provide a unidirectional voltage.

9. An electronic musical instrument comprising a plurality of audio tone producing circuits, means for causing, when manually operated, said tone producing circuits to produce said tones, means for connecting said producing circuits to said causing means, electrode means for detecting the muscular voltage produced by at least one muscle on a human body, means for varying an audio characteristic of the tones produced by at least one of said circuits as a function of said detected muscular voltage and means for connecting said varying means to said electrode means and to said producing circuits.

10. An instrument as in claim 9 including means for amplifying said detected muscular voltage to produce a control signal.

11. An instrument as in claim 10 including means for reCtifying the amplified voltage to produce said control signal.

12. An instrument as in claim 9 wherein said varying means includes means for varying the amplitude of said tones as a function of said muscular voltage.

14. An instrument as in claim 9 wherein said varying means includes the means for imparting a tremolo effect as a function of said muscular voltage.

18. An instrument as in claim 9 wherein said causing means includes a plurality of keys each operatively connected to one of said tone producing circuits.

19. A method of operating an electronic musical instrument of the type having a plurality of audio tone producing circuits and means for manually operating said circuits to produce audio tones comprising the steps of: manually operating said tone producing circuits to produce said tones, detecting the muscular voltage produced by at least one muscle on a human body, generating a control signal from said muscular voltage, applying said control signal to said tone producing circuits, and varying an audio characteristic of the tones produced by at least one of said circuits as a function of said control signal.

20. A method as in claim 19 including the further step of amplifying said detected muscular voltage to produce a control signal. 21. A method as in claim 20 including the further step of rectifying the amplified voltage to produce said control signal.

24. A method as in claim 19 wherein said step of varying includes the step of imparting a tremolo effect as a function of said muscular voltage.