05/042155

05/16/1972

06/01/1970

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Columbia Broadcasting Systems, Inc. (New York, NY)

84/721

984/328, 307/119

G10H1/14; G10H1/06; G10H3/00

84/1.01,1.08,1.11,1.19,1.22,1.24,229LD,229B,DIG.19,229P,229PC,229F,1.26 178/7.3 179/1SW 307/119 333/17

3553337	CIRCUIT ARRANGEMENT FOR IMITATING THE TOUCH OF MUSICAL INSTRUMENTS WITH PERCUSSION	January 1971	Dijksterhuis
3558793	EXPRESSION PEDAL ASSEMBLY FOR AN ELECTRONIC MUSICAL INSTRUMENT PREFERABLY WITH PRESSURE AND/OR LIGHT SENSITIVE SENSORS	January 1971	Nakada
3567839	PERCUSSIVE ELECTRONIC MUSICAL INSTRUMENT WITH OUTPUT LEVEL CONTROLLED BY INTENSITY OF KEY DEPRESSION	March 1971	Dijksterhuis
3530224	FOOT CONTROLLED CONTINUOUSLY VARIABLE PREFERENCE CIRCUIT FOR MUSICAL INSTRUMENTS	September 1970	Plunkett et al.
2953958	Electronic musical instrument control system	September 1960	George
3176060	Gating system for electrical musical instrument	March 1965	Bissonette et al.
3178499	Electronic musical instrument	April 1965	Peterson
3268658	Transistor clamp circuit	August 1966	Schroeder et al.
3300569	Electronic organ	January 1967	Cunningham
3213181	Tone modifier for electrically amplified electro-mechanically produced musical tones	October 1965	Snoddy et al.
3519720	ORGAN HAVING VARIABLE TIMBRE WITH TRANSISTORIZED PLAYER CONTROLLED DYNAMIC FILTER	July 1970	Bunger
2986953	Foot pedal	June 1961	Armond et al.

Myers, Lewis H.

Weldon U.

I claim

1. For use with an electrical musical instrument,

2. The apparatus of claim 1 including

3. The apparatus of claim 1 including

4. The apparatus of claim 1 including

5. The apparatus of claim 4 wherein said variable impedance devices are field effect transistors.

6. In combination,

7. The combination of claim 6 including means for momentarily retaining said formant circuit enabled and said second circuit disabled after termination of motion of said control.

8. The combination of claim 6 including

9. In combination,

10. The method of automatically actuating first and second sound control circuits for a musical instrument, said circuits being connected in parallel, said method comprising the steps of

11. A control circuit comprising

12. The control circuit of claim 11 wherein said means for enabling said modulating circuit and said means for disabling said second circuit comprises

13. The circuit of claim 12 including

14. Apparatus for handling a musical signal comprising

15. The apparatus of claim 14 including

16. The apparatus of claim 14 wherein said first circuit is a formant circuit having a frequency response peak that varies with position of said operator.

17. The apparatus of claim 15 wherein said operator is movably mounted, said first circuit comprising

18. A control circuit comprising

19. The circuit of claim 18 including

20. For use with an electrical musical instrument first and second circuits adapted to pass a musical input signal,

21. The apparatus of claim 20 wherein said first circuit includes

22. The apparatus of claim 21 wherein said switching means comprises

23. The apparatus of claim 22 including

24. The apparatus of claim 21 including

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to motion operated circuits and more particularly concerns a motion operated special effects circuit for a musical instrument and a control therefor.

Description of Prior Art

In electric musical instruments such as the string, percussive and wind instruments, including the electric organ, several different types of voicing or tone color circuits are employed to produce different sound effects. Generally, such circuits are employed alternatively. Pedal controlled switches are provided to enable selection of a given one of such circuits. Among such circuits are special effects circuits such as the formant circuit that is employed to simulate, for example, the sound made by a trumpet player as a mute is moved into and out of the trumpet bell. Such a special effects circuit embodies a variable potentiometer of which the wiper is caused to oscillate or move to and fro to thereby shift the peak frequency response of the circuit through the frequency spectrum. The operating or controlling potentiometer of such a circuit is physically connected to a foot pedal which, as it is rocked, causes the special effect. When the formant circuit is not being used, its controlling potentiometer is preferably in a central or neutral position and an alternative circuit is employed.

In present arrangements, a special switch on or closely adjacent the foot pedal must be operated to respectively enable and disable the special effects formant circuit. If, as commonly occurs, the operator completes playing a passage employing special effects of the formant circuit, but fails thereafter to operate the formant circuit disabling switch, subsequent passages will be modified by the formant circuit and its operative potentiometer which may not have stopped in a null or central position. Accordingly, subsequent passages will be either attenuated in power or shifted in frequency response.

Various arrangements for foot pedal controlled switches in a musical instrument are illustrated in U.S. Pat. No. 2,953,958 to T. J. George, but no automatic operation of a motion operated control is shown. U.S. Pat. No. 3,176,060 to A. J. Bissonette, et al., teaches the use of gating devices or switches for an electrical musical instrument that can provide a gradual onset of a variety of reproduced tones. Other switching arrangements for circuitry of electric musical instruments are shown in U.S. Pat. No. 3,374,316 to M. A. Slaats, et al., who employs the impedance of photo cells responsive to a switch operated light source for alternatively selecting one of a pair of musical sources. None of the arrangements of the prior art recognize the problem of motion operated control of special effects circuits and, accordingly, suggest no solution.

An object of this invention is to provide a solution to this problem and achieve a motion operated control for an electrical circuit that automatically turns itself on and off.

SUMMARY OF THE INVENTION

In carrying out principles of the present invention in accordance with a preferred embodiment thereof, a signal modulating circuit includes a movably mounted operating member connected to cause the circuit to modulate upon motion of the operating member. Not only does the circuit modulate in response to motion of the member, but it is also turned on during such motion. In a specific embodiment of the invention, an automatic on-off switch is connected in circuit with both a special effects circuit and an alternate circuit or signal path. Oscillation of a control for the special effects circuit automatically enables the latter and disables the alternate path.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an electric musical instrument embodying an automatically controlled formant circuit in accordance with principles of the present invention,

FIG. 2 illustrates a foot pedal control for the instrument of FIG. 1 and

FIG. 3 comprises a circuit diagram of the automatic switching arrangement of the circuit of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT

As illustrated in FIG. 1 an electric musical instrument 10, such as a guitar having a number of strings and a transducer or pickup, provides an electrical signal output that represents the particular musical tone obtained from the instrument string. Although the present invention may most commonly be employed with an electric guitar, it will be readily appreciated that the described principles and circuitry may be employed with any type of electrical instrument, whether stringed, percussive, wind, or the like, that provides an electrical signal on an output lead such as lead 12 representing the desired musical tone. Such instrument need not be limited to a type including a vibratile or vibratory member and a pickup therefor that generates the musical tone, but may be of the general type that provides electrical generation of a variety of tones such as the conventional electric organ or an instrument employing percussive effect of the electric piano.

The electrical signal generated by the instrument is normally supplied to a conventional preamplifier circuit 14 from whence it may be fed via a lead 46 to an output amplifier 16 and speaker 18 through a signal shaping or alternate circuit 20. Such an alternate circuit may be one of many different types that provides any of several well known tone expression, volume control, or modifying circuits. For example, various types of voicing circuits, tone control, volume control or other special effects circuits may be used in the alternate path. In many applications no alternate signal shaping is desired, wherefor the alternate path performs no function other than to feed the signal from the amplifier 14 to the output amplifier and speaker. Where the circuit 20 includes different types of circuits, these may be alternatively selected by means of a conventional switching arrangement (not shown).

In order to provide for special effects in the form of continuous shifting of the peak of the frequency response of the electrical signal handling circuitry through the frequency spectrum, there is provided a conventional formant circuit 22 that includes a variable potentiometer (not shown in FIG. 1) of which the wiper arm is reciprocated or oscillated by a reciprocating or oscillating motion of a foot pedal control 24. The output of both the alternate circuit 20 and the formant circuit 22 are fed through an automatic switch 26, through which all of the signals are supplied to the output amplifier and speaker 16, 18.

In general, when the formant circuit is being employed, the alternate circuit 20 is not employed, and substantially all of the signal is fed from preamplifier 14 through the formant circuit and thence through the output amplifier. Alternatively, when the formant circuit is not being employed, desirably this circuit is not operable upon the tone signal, and all of the signal is sent through alternate circuit 20 to the output amplifier.

The formant circuit is operable by causing a rocking motion of foot pedal control 24. In accordance with the present invention, the automatic switch 26 is interposed between the input of output amplifier 16 and the output of both the formant circuit 22 and the alternate tone circuit 20, so as to provide automatic alternative operation of circuits 20 and 22, each to the exclusion, or substantial exclusion, of the other. To this end, the automatic switch involves a derivative action and is, in effect, a derivative circuit that responds to velocity or change of position of the control 24 to pass the output of formant circuit 22 when and only when the pedal control is in motion. Simultaneously, switch 26 disconnects the output of alternate circuit 20. When motion of foot pedal control 24 ceases, the switch 26 automatically returns to its normal position wherein the output of alternate circuit 20 is coupled to amplifier 16 and the formant circuit 22 is disabled.

Thus, with the illustrated arrangement, the player does not have to perform any specific operation to switch from use of the alternate circuit to the formant circuit and vice versa, nor does he have to operate any particular switch to enable or disable the formant circuit. When a particular passage being played calls for operation of the formant circuit, the player merely performs the usual rocking or oscillation of the foot pedal. This normal operation automatically enables the formant circuit and disables the alternate circuit. When operation of the foot pedal is stopped, the arrangement automatically goes back to its normal position wherein the formant circuit is disabled and the tone signal is passed through circuit 20.

Illustrated in FIG. 2 is a substantially conventional arrangement of oscillating or rocking foot pedal control 24 for the formant circuit. A substantially rectangular open-top housing 28 carries a treadle member 30 that is pivoted to the housing by a shaft 32 for bi-directional or rocking motion around the pivot as indicated by the double-ended arrow 34. Carried within the housing 28 is an electronics package 36 that may constitute a microcircuit or other miniaturized arrangement of substantially all or part of the preamplification, switching and other circuits of FIG. 1. The housing 28 mounts three rotary potentiometers 38 that are electrically connected by a cable 40 to electronics package 36 as will be more particularly described hereinafter in connection with the description of FIG. 3. The three potentiometers 38, fixedly carried within the housing 28, have a common operating shaft to which is affixed a gear 42. The latter meshes with a toothed rack 44 carried by treadle member 30 and depending therefrom into operative engagement with the teeth of gear 42. As the treadle member 30 is oscillated about pivot 32, the rack 44 reciprocates through a vertically oriented arcuate path and effects a back and forth oscillatory rotation of gear 42. Accordingly, the three rotary potentiometers 38 have their wiper arms oscillated by the rocking action of the treadle 30.

Illustrated in FIG. 3 is the circuit of the automatic switch 26 of FIG. 1. The musical tone signal from preamplifier 14 appears at lead 46 whence it is fed as an input to both the formant circuit 22 and the alternate circuit 20. At the outputs of circuits 20 and 22 are series and shunt variable impedance or switching devices in the form of field effect transistors 48 and 50, respectively. These devices, which may be junction field effect transistors such as No. F1175 made by Union Carbide, for example, have a normally low impedance between the source and drain electrodes thereof, on the order of about 1,500 ohms. Upon receipt of a negative signal to the gate electrode thereof, the impedance of the device increases rapidly, and to a large value which may, for practical purposes, approach infinity.

The output of circuit 22 is fed through a pair of series connected resistors 52, 54 and thence to a terminal 56 which, together with ground terminal 57, forms the output of the automatic switching device. The shunt field effect transistor 50 has one of its drain and source electrodes connected to the junction between resistors 52 and 54 and the other of its drain and source electrodes connected to ground as indicated in FIG. 3. The drain and source electrodes of the series switching field effect transistor 48 are connected in series between the output of tone circuit 20 and the automatic switch output terminal 56. In addition, such drain and source electrodes of transistor 48 are connected to ground via resistors 58 and 60, respectively. A variable resistor 62 is connected across these electrodes of transistor 48 to provide an adjustable minimum value of the impedance of this device whereby some of the signal fed through alternate circuit 20 may be mixed with the output even when formant circuit 22 is in operation.

Formant circuit 22 conventionally includes a potentiometer 64 having a wiper arm 66 connected to be operated as indicated by dotted line 68 by rocking of the treadle 30. Thus, whenever the formant circuit is to be employed, the treadle 30 is oscillated, wiper arm 66 of the formant circuit moves back and forth across the resistance of the potentiometer 64, and the peak frequency response of the output is caused to move back and forth through the frequency spectrum.

One such formant circuit is combined with a "fuzz" circuit and sold as the "FENDER FUZZ-WAH" unit, described on page 31 of the 1969 catalog of Fender Musical Instruments of Santa Ana, California. The formant or "wah" circuit basically comprises a parallel inductance capacitance circuit in which a signal component of variable phase angle is controlled by position of the potentiometer wiper.

In order to operate series and shunt switches 48 and 50 automatically upon occurrence of motion (e.g., change of position) of treadle 30, there are provided first and second oppositely poled switch operating potentiometers 70, 72, each having its wiper arm connected to be operated by the same treadle motion input as indicated at 68. The three potentiometers 66, 70, and 72 are those collectively illustrated at 38 in FIG. 2 and are all mounted within the housing 28. Preferably, all potentiometers have a common operating shaft so that all are ganged for operation upon rocking of treadle 30. Potentiometers 70 and 72 are energized in opposite sense by means of dc source such as a battery 74. As the wiper arms of potentiometers 70 and 72 are moved together downwardly in the illustration, for example, the voltage on the wiper of potentiometer 70 goes more positive. Simultaneously the voltage on the wiper of potentiometer 72 goes more negative.

For potentiometer 72, the negative going voltage on its wiper arm that occurs during one direction of motion of treadle 30 is coupled through a capacitor 76, across a resistor 79, having one end connected to ground, and thence through a diode 78 to the gate electrodes of both the series and shunt field effect transistors 48 and 50. Similarly, upward motion of the wiper arm of potentiometer 70 provides a negative going voltage that is coupled through a capacitor 80, across a resistor 82 having one end grounded, and through a diode 84 to the gate electrodes of both of the switching devices 48, 50.

Because of the polarity of both of the diodes 78, 84, only negative going voltage changes on the wiper arms of potentiometers 70, 72, can be passed to the gate electrodes of the switching transistors. So, too, it will be observed that the coupling capacitors 76 and 80 allow the gate electrodes of the switching transistors to receive a signal from the potentiometers only during motion of the wiper arms thereof, since the capacitors, of course, block dc signals. Furthermore, the illustrated arrangement allows transmission of a changing signal from only one of the potentiometers for a given direction of motion of treadle 30 and potentiometer wiper arms.

For example, as the wiper arms of both potentiometers 70 and 72 move downwardly in FIG. 3, the voltage on the arm of potentiometer 70 increases and, accordingly, is blocked by diode 84. However, the voltage on the arm of potentiometer 72 concomitantly decreases and, accordingly, a negative going voltage is coupled via capacitor 76 through diode 78. On the other hand, when the two potentiometer arms are moved in the other direction, upwardly in FIG. 3, the positive going voltage on the wiper arm of potentiometer 72 is blocked and a negative going voltage on the arm of potentiometer 70 is coupled to the gate electrodes via diode 84.

Thus, no matter which way the treadle 30 is moving one or the other of the potentiometers 70, 72 couples a negative going signal to the gate electrodes of both field effect transistors 48 and 50 whereby the impedance of both of these is increased when the treadle is moved. Accordingly, whenever formant circuit 22 is operated by rocking motion of the treadle 30, the impedance of switching device 48 increases to attenuate or block the output of circuit 20. At the same timer, the impedance of shunting switch 50 increases to allow the output of formant circuit 22 to pass through resistor 54 to the automatic switching device output terminals 56, 57, instead of passing to ground. The values of resistors 52, 54 and 58, 60 are considerably greater than the value of the impedance of the field effect transistors 48 and 50 when the latter are in their low impedance state. When in their high impedance state, the switching devices have a resistance considerably greater than the values of resistors 52, 54, 58 and 60.

The described circuit has a derivative type action that provides a signal only upon and during motion of the foot pedal control. It may be modified in order to round off, in effect, the otherwise relatively sharp on-off action that accompanies initiation and termination of foot pedal motion. Thus, it is desired to maintain the formant circuit operating for a short period of time after termination of foot pedal motion. Further, as the foot pedal reverses its direction, and the arms of potentiometers 70, 72 reverse direction, the control signal is shifted from one path such as, for example, that including capacitor 76 and diode 78, to the other path of the circuit, that including capacitor 80 and diode 84. Each such diode has a voltage or conduction threshold of about a 0.65 volts. Accordingly, upon reversal of direction of motion of the potentiometer arms, the transmission of signal through one of the diodes 78, for example, is stopped, but transmission of the signal through the other diode 84 cannot begin until the motion in reverse direction has progressed sufficiently to overcome the forward conduction threshold of the previously non-conducting diode 84. This could result in a decrease in the negative signal applied to the gates of the field effect transistor switches and achieve a momentary switching of the signal from formant to alternate circuit.

To avoid this undesired momentary switching, and to provide a selectively variable extension of the time of automatic switch operation, the anodes of both diodes 78 and 84 are connected to ground via a parallel RC circuit comprising a capacitor 86, a fixed resistor 88 and a variable resistor 90. Thus, any negative going gate control signal passed through either of diodes 78 or 84 is stored in capacitor 86 to maintain the gate electrodes sufficiently negative after motion of the arms of potentiometer 70 and 72 is stopped.

The period of extension of switch operation is controlled by the value of the resistance in the discharge path of capacitor 86, since the charge on the capacitor will leak off through resistors 88 and 90. For example, capacitor 86 may be on the order of 0.1 microfarads, resistor 88 may be about 2 megohms, and resistor 90 may be variable between 2 and 20 megohms. With resistor 90 at its maximum value, the switches 48 and 50 will continue to operate for as long as 5 seconds after termination of motion of the potentiometer arms. With resistor 90 at its minimum value of about 2 megohms, delay in operation of switches 48, 50 is substantially negligible. Even at minimum value of resistor 90, sufficient delay exists to accommodate the dead time of control signal that would otherwise occur at the instant of reversal of the direction of motion of the potentiometer wiper arms.

When the foot pedal control is operated to rock the wiper arms of the three ganged potentiometers 64, 70, 72, a desired signal is provided at the output of formant circuit 22 and the impedance of switch 48 goes so high as to completely block the output of circuit 20. In some situations, it may be desirable to retain a portion of the output of circuit 20, although attenuated, even during the operation of formant circuit 22. To this end, there is provided the variable resistor 62 connected across the drain and source electrodes of series switch 48 whereby the total impedance across these terminals will not go above a predetermined level as controlled by adjustment of resistor 62. Accordingly, no matter how high the impedance of switch 48 may be, the resistance 62 may be adjusted to allow a desired portion of the output of circuit 20 to be mixed with the output of formant circuit 22 during operation of the latter.

It will be readily appreciated that a variety of different arrangements of the pair of switching devices 48, 50 may be employed without departing from principles of the present invention. Fundamentally, the switching devices 48 and 50 are variable impedance devices and are of a type and are connected to provide a mutually opposite sense impedance variation in the formant and alternate circuits when the foot pedal is oscillated. Both switching devices may be series connected or both may be connected in shunt if opposite conductivity types are employed, or if provision is made to reverse polarity of the signal applied to one. Similarly, instead of locating one or both of switches 48, 50, at the output of the formant and alternate circuits, these may be positioned at the input of such circuits, or voltage controlled impedance devices may be employed within the formant or tone control circuits themselves. Furthermore, only one of potentiometers 70, 72 is needed if diodes 78, 84 are oppositely poled, both connected to the same potentiometer wiper arm, and switching transistors of opposite polarity types are used. Any one of these or other arrangements may be implemented to provide automatic enabling of the formant circuit and concomitant automatic disabling of tone control or other alternate circuit, either completely or partially, when and only when the foot pedal control is in motion. Further, although field effect transistors are preferred as variable voltage controlled impedance devices, it will be readily appreciated that a variety of other types of transistors and other types of voltage controllable impedances may be employed.

In some applications other special effects circuits are employed with the formant circuit. For example, a circuit known as a "fuzz" circuit introduces a particular type of intentional distortion, in effect increasing the overtone content by its non-linearity. Such a "fuzz" circuit may be connected in series with the illustrated formant circuit and suitable switching provided to allow any one of the "fuzz," formant or alternate circuits to be used individually, or to feed the input to the formant circuit through the "fuzz" circuit. Other combinations are readily available as may be deemed necessary or desirable.

In such arrangements, any additional circuit, such as a "fuzz" circuit, that is connected in series with, and ahead of the formant circuit, would be indirectly controlled by operation of the illustrated automatic switching.

The arrangement of potentiometers 70 and 72, ganged for operation together with the operation of potentiometer 64, is a preferred form of simple, reliable and efficient motion actuated signal generator. Many other devices are well known to those skilled in the art for generating a signal upon or in response to an input mechanical motion. Various types of magnetic devices employing a relatively movable magnet and coil, piezoelectric devices responsive to pressure on the pedal, and variable capacitance devices are among elements well known to those skilled in the art that are capable of generating a control signal in response to an input mechanical motion. Variable impedance photo cells such as shown in the above-mentioned patent to Slaats, et al, may be employed as the switches of the automatic switching device and caused to receive illumination when the foot pedal control is operated.

There has been described an improved automatic on-off control for circuitry of an electrical musical instrument wherein a special effects circuit is caused to be operated by substantially continuous motion of a movable control member. The special effects circuit and a parallel alternative circuit path for electrical signals are automatically enabled and disabled respectively when and only when the movable operating member of the special effects circuit is in motion. Thus, the instrument player need not directly switch in or out the special effects circuit, but simply upon operation thereof, the desired switching is automatically established.

The foregoing detailed description is to be clearly understood as given by way of illustration and example only, the spirit and scope of this invention being limited solely by the appended claims.