US3657463A

US3657463A - Keyer control circuit for electronic musical instruments

Info

Publication number: US3657463A
Application number: US90294A
Authority: US
Inventors: Ryu Hiyama
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1969-11-18
Filing date: 1970-11-17
Publication date: 1972-04-18
Anticipated expiration: 1989-04-18

Abstract

In an electronic musical instrument including playing keys and respectively associated tone keyers, each tone keyer is keyed by a control signal producing circuitry. The control signal producing circuitry comprises a coil inducing an electromotive force responsive to the depressing speed of the associated key having a magnet, a capacitor charged with the induced electromotive force through a first diode, a discharging circuit consisting of a second diode and a resistor, the second diode being connected in the forward direction for a discharging current of the capacitor, and a normally open switch associated with the key and connected between the juncture of the second diode and the resistor and a voltage source for reversely biasing the second diode, wherein the control signal for the tone keyer is derived from the capacitor. This construction prevents the instrument from producing cipher which would otherwise occur due to the failure of closure of the switch which is associated with the key.

Description

0 United States Patent 1151 3,657,463 Hiyama [451 Apr. 18, 1972 54] KEYER CONTROL CIRCUIT FOR 3,544,695 12/1970 Dijksterhuis ..s4/1.13 ELECTRONIC MUSICAL 3,553,337 1/1971 Dijksterhuis ..84/l.13 INSTRUMENTS Primary Examiner-Laramie E. Askm Inventor! 'Y Hamamatsu- P Assistant Examiner-Stanley J. Witkowski [73] Assignee: Nippon Gakki Suzo Kabushiki Kaisha, Anomeycushman Darby Cushman Hamamatsu-shi, Japan [57] ABSTRACT [22] Filed: Nov. 17, 1970 In an electromc mus1cal instrument including playing keys and PP No.1 90,294 respectively associated tone keyers, each tone keyer is keyed by a control signal producing circuitry. The control signal [30] Foreign Application Priority Data producing circuitry comprises a coil inducing an electrometlve force responsive to the depressing speed of the associated Nov. 18, 1969 Japan ..44/92253 key having a magnet, a capacitor charged with the induced 1969 Japan 3 3 --44/92254 electromotive force through a first diode, a discharging circuit Nov. 18, 1969 Japan ..44/109351 consisting ofa second diode and a resistor, h second diode 1 being connected in the forward direction for a discharging [5%] [1.8.5] ..84/1-26, 84/l.l3 currem of the capacitor and a normally open Switch 2 gi 1/072 sociated with the key and connected between the juncture of 1 0 care the second diode and the resistor and a voltage source for reversely biasing the second diode, wherein the control signal [56] References Cited for the tone keyer is derived from the capacitor. This construction prevents the instrument from producing cipher UNITED STATES PATENTS which would otherwise occur due to the failure of closure of the sw1tch which 1s associated with the key. Re.27.0l5 12/1970 Di ksterhuis et a1 ..84/1.15 3,567,839 3/1971 Dijksterhuis ..84/l.26 7 Claims, 13 Drawing Figures 8A K TONE ,1, L o. Q 'O rm XI. KEYER Patented April 18, 1972 3 Sheets-Sheet 1 FIG,

TONE KEYER FIG. 2

SAI

TONE KEYER 7 IN NTOR.

flTTo/a A1575 Patent ed April 18, 1972 3,657,463

3 Sheets-Sheet 2 T|ME-- FIG. 6 FIG. 40 0 FIG. 4b

OUTPUT SIGNAL LEVEL HTTDRIUEY Patented April 18, 1972 3,657,463 5 Sheets-Sheet :3

FIG. 7 J'ILT; A

TONE +Vcc "H to J I 5L; 2 g5 2 INVE TOR.

MM) AMYYW HTfORII EYS BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a keyer control circuit for electronic musical instruments, and more particularly, to an improved keyer control circuit in a keying system for the instrument of the type described and capable of producing the so-called touch-responsive tone envelope effect such that a keyed tone signal has an amplitude or tone envelope in accordance with the intensity of depression of an associated key, i.e., the depressing speed of the key.

2. Description of the prior art Recently, there has been proposed an arrangement of a touch-responsive tone envelope control circuit for an electronic musical instrument having a keyer tone control circuit therein, which comprises a coil directly grounded at one end thereof and adapted to vary the interlinking magnetic fluxes in association with the depression of a playing key arranged on a keyboard of the instrument, e.g., the key carrying a magnet thereunder, the other end of said coil being grounded through a series circuit of a rectifying element such as a diode and a capacitor for storing an electromotive force induced in the coil responsive to the key depressing, and a key-operated normally closed switch having a movable contact connected between the capacitor and the diode and a stationary contact grounded through a resistor and capable of being actuated in association with the operation of the associated key, the movable contact being also connected to a control terminal of a keyer circuit for receiving a control signal from the arrangement and thereby triggering the keyer. In such an arrangement, however, a fear for the occurrence of cipher has been unavoidable due to the failure of a perfect closure of the contact of the above-mentioned normally closed switch. even when the switch is not actuated by the associated key, resulting in an extremely bad effect of the music being played.

SUMMARY OF THE INVENTION It, therefore, is the principal object of the present invention to provide an improper keyer control circuit for use in a keying system of an electronic musical instrument, which is capable of completely preventing occurrence of cipher due to trouble of the switch contact.

Another object of the present invention is to provide an improved keyer control circuit capable of securely and reliably controlling a keyer in association with depressing of a corresponding key.

A further object of the present invention is to provide an improved keyer triggering circuit which makes it possible to provide a so-called touch-responsive tone envelope effect of an improved respondence of the tone intensity to the key depressing speed.

A still further object of the present invention is to provide a keyer triggering circuit capable of operating in close response to even the slowest speed of the key depression.

Other objects, features and advantages of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic circuit diagram illustrating an embodiment of the present invention.

FIG. 2 is a schematic circuit diagram illustrating another embodiment of the present invention.

FIGS. 3a to 30 and FIGS. 4a to 4c are graphs for explaining the functions of the circuits shown in FIGS. 1 and 2, respectively.

FIGS. 5 and 7 are schematic wiring diagrams illustrating other embodiments of the present invention.

FIGS. 6 and 8a and 8b also are illustrations for explaining the functions of the circuits shown in FIGS. 5 and 7, respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereunder, like symbols and references indicate like parts in the drawing.

Referring to FIGS. 1 and 3, a tone keyer control circuit according to an embodiment of the present invention will be described, in which L designates a coil grounded at one end thereof and arranged to vary the interlinking magnetic fluxes in association with depression of an playing key K arranged on a keyboard of an'electronic musical instrument, which key carries a magnet thereunder, and the other end of said coil is grounded through a rectifying element D and a capacitor C both being connected in series to each other. The juncture d between the element D and the capacitor C is grounded through a series circuit consisting of a unidirectional element Do and a resistor R the connection point r between which is connected via a make switch S, Le, a switch having a normally open contact associated with the key K and operative responsive to the key depression to a DC power source +Vcc. The juncture dis also connected to a control terminal of a known tone keyer circuit SA which may be constituted by gating elements such as diodes and FETs (field effect transistors) and of which the detail will be omitted here. The tone keyer circuit SA is provided with its input terminal tl adapted to receive tone signal and its output terminal to adapted to derive that tone signal as its output signal in association with the depression of the key.

Thus, the number of the tone keyer control circuits and the keyer circuits SA which are installed in the console of the instrument corresponds in number to tone generators (not shown) or the playing keys, for example, sixty-one.

In operation, when any one key K provided in the instrument is depressed, amagnetic member-which may be either magnetized or not magnetized and which may be attached to the key-moves toward or away from the fixed coil L, thereby resulting in a damped pulse voltagewhich is approximately proportional to the intensity or the speed of depression of the playing key-due to variations in interlinking fluxes established around the coil, as shown by a waveform in FIG. 3a. The induced voltage would theoretically be a DC pulse, but as a matter of fact the voltage presents an alternating shape due to bound of the key, a stray capacity of the coil, etc. The induced alternative voltage is rectified through the diode D and as a result, positive DC components developed at the diode D are stored in the capacitor C, as shown by curves in FIG. 3b. At the same time, the make switch S is closed in response to the key depression to reversely bias the unidirectional element Do at positive voltage of the power source +Vcc, which is rendered to be non-conducting, and as a result, the voltage stored on the capacitor C is kept at the control terminal of the tone keyer SA, so that a tone signal applied to the input terminal t1 may be successively derived at the output terminal to at a level corresponding to the depressing speed of the key as shown by curves in FIG. 3c until release of the key.

Then, upon release of the key being depressed, the key is made restored by its self-retum action and simultaneously, the switch S is opened, so that no reverse bias voltage is applied across the unidirectionally conducting element D0, which element is rendered in its conducting state and therefore, the charge stored on the capacitor C at a voltage induced in response to the depressing speed of the key discharges in a short period of time through the element D0 and the resistor R having a relatively low resistance. As a result, the gating element in the keyer circuit SA is reverse biased into its non-conducting state, and hence, no tone signal is developed at the output terminal to.

In the operation of the depressing key, an oscillative voltage induced in the coil L is responsive to the intensity of depression of the key K or the depressing speed of the key in magnitude. Accordingly, a quick or strong key depression makes the storage voltage of the capacitor C higher to render the tone output level at the keyer greater, while a slow or weak key depression brings a small tone output level. Thus, the present arrangement makes it possible to achieve a keyer control with so-called touch-responsive tone envelope effects in the electronic musical instrument. For example, this arrangement permits to provide a piano play effect.

Referring to FIG. 2, there is shown another embodiment of the present invention, in which the circuit connection is somewhat different from that of FIG. 1. That is, one end of a coil L1 is connected to the power source +Vcc and the other is grounded through a rectifying element D1 and the capacitor C1 all connected in series. The connection point d1 between the element D1 and the capacitor C1 is connected via a series circuit of the unidirectionally conducting element D and the resistor R1 to the power source +Vcc. At the point r1 between the element D10 and the resistor R1 is connected the key actuated normally open change-over switch S1 whose opposite end is grounded. The connection point d1 is also connected to the control terminal of the gating element in said keyer circuit SAl. In this case, the gating element is of the type in which it makes a non-conducting state when its control electrode being above a predetermined positive potential.

The operation of the arrangement will be described similarly to the preceding embodiment.

Initially, in the inoperative condition of the normally open switch S1, the capacitor C1 is supplied with a positive voltage via the resistor R1 and the unidirectional conducting element D10 from the power source +Vcc and charged at that voltage. At that time, the gating element of the keyer circuit SA! is in its non-conducting state, and accordingly, no output signal is developed at the output terminal r10 of the keyer SAl.

When the key K is depressed a damped pulse voltage-is produced across the coil L as shown by a waveform in FIG. 4a, as similarly as described above. During the negative half wave duration of the produced voltage, the positive voltage stored on the capacitor C1 is discharged via the rectifying element D1, thus dropping the voltage across the capacitor C1. At that time, the switch S1 is also actuated to close its contact with the point r1 being rendered at the ground potential, so that the diode D10 is rendered in its non-conducting state to shut the power source off from the capacitor C1. Accordingly, the voltage across the capacitor C1 takes waveforms as shown in FIG. 4b having a drop portion lower than the initially charged voltage, whereby the conduction of the gating element of the keyer SA] is controlled. Thus, it will be seen that the tone input signal applied to the keyer SAl can be derived at the output terminal r10 in response to the key depression, as shown by waveforms in FIG. 4c.

Upon release of the key being depressed, the switch S1 is made open to forward bias the diode D10 into its conducting state. Then, the capacitor C1 can be charged from the power source +Vcc and accordingly, the voltage across the capacitor C1 is increased above the predetermined voltage at which the gating element of the keyer SA] is rendered in its non-conducting state. Thus, the keyer is shut off by release of the depressed key.

FIG. 5 shows a modification of the preceding embodiments which comprises a transistor Q as a class amplifier to amplify a voltage induced across the coil L in response to the depressing speed of the key. The base of the transistor Q is grounded through the coil L, the emitter is grounded through a resistor R and the collector is connected through a load resistor R3 to a relatively high direct current voltage source +Vcc and through a series circuit of a diode D2 and a resistor R2 to a relatively low DC voltage source +Ve, e.g., half of +Vcc whereby the keyer SA can be controlled to provide the tone volume responsive to the key depressing speed in two rates depending on the ranges of the depressing speed of the key. The collector is also connected through a diode D in the forward direction for a negative going pulse to a grounded capacitor C. The juncture point a is connected to a gate control terminal of the keyer SA. The gate control portion of the keyer circuit SA is normally held at a relatively high voltage by the capacitor C being fully charged, at which the gating element is rendered in its non-conducting state. The capacitor C is charged through a diode D1 and a resistor R1 by the DC power source +Vcc upon opening of the key-actuated normally open switch S, i.e., a make switch. The circuit operation of this arrangement can be said to be effected as shown in FIGS. 3a, 4b and 4c. When the key K is depressed a damped pulse voltage is produced across the coil L as shown by a waveform in FIG. 3a. The positive cycles of the voltage are amplified by the transistor 0 into negative going cycles at the collector. These negative going voltages discharge through the diode D the capacitor C which has been normally charged up to +Vcc through the resistor R1 and the diode D1. Accordingly, the voltage at the point d goes down as shown in FIG. 4b, which in turn gates the tone signal as shown in FIG. 40. Within a certain range of the depressing speed of the key, i.e., where the negative peak of the collector voltage does not go below +Ve, the diode D2 never conducts and accordingly the volume is controlled by the depressing speed at a higher rate. But over that range, i.e., where the negative peak of the collector voltage go below +Ve, the diode D conducts and accordingly the volume is controlled by the depressing speed at a lower rate.

In FIG. 6, the relation between the key depression speed and the output volume is shown, in which a chain line is desirable and a solid line is undesirable to provide effects playing piano. This is due to the selection of the values of the elements and the potential of the DC source +Ve.

Referring to FIG. 7, there is shown a further modification of FIG. 5, which is characterized by a circuit used in common to all keyer control assemblies, as shown by a block E for improving the linearity of the output of each transistor and automatically effecting thermal compensation for the transistor, in place of having the series circuit of the resistor R2 and the diode D2 connected to the DC source +Ve as shown in FIG. 5. That is, the coil L is grounded through a parallel circuit composed of a diode D2 and a capacitor C2 at its one end opposite to that connected to the base of the transistor Q. Said one end of the coil L is connected through a resistor R4 to the DC voltage source +Vcc. The line 1 is kept at a certain small voltage due to the forward voltage drop of the diode D2.

Thus, a predetermined voltage is applied to the base of the transistor, and the characteristics of its base-emitter voltage VBE vs. its base current 15 which would otherwise be of a solid line in FIG. 8a is compensated to be as a chain line in FIG. 8a, and as a result the characteristics of the output signal level vs. the depressing speed of the key which would otherwise be of a solid line in FIG. 8b is compensated to be as a chain line in FIG. 8b, thereby eliminating a non-sensitive region of the key depression. The diode D2 acts as a thermal compensation for the transistor 0 as well known in the art. The elements having the same references as FIG. 5 are of the same functions.

I claim:

1. A tone keyer control circuit for use in an electronic musical instrument having at least a manually depressable single playing key having a magnet mounted thereon and at least a single tone keyer comprising:

a coil for mounting adjacent said key so that depression of said key induces a voltage signal in said coil having an amplitude which varies with the speed with which said key is depressed,

a first diode connected to said coil for receiving and rectifying said induced voltage,

a capacitor connected to said first diode so as to change its voltage from an initial voltage in response to the rectified signal,

an initial voltage return circuit connected to said capacitor comprising a serially connected resistor and second diode connected so that current normally flows through said capacitor via said second diode and register when said capacitor voltage is changed to return said capacitor voltage to its initial voltage,

a first terminal adapted for receiving a direct current voltage,

plurality of transistors, each transistor having a base cona normally open switch mounted so at to close by the depression of said key and connecting the junction between said second diode and said resistor to said first terminal,

means for providing a voltage at said first terminal so that 5 said second diode is reverse biased to prevent flow of current through said second diode, which would cause the voltage of said capacitor to return to its initial voltage, so long as said switch remains closed, and

means for connecting said capacitor to said tone keyer.

2. A circuit as in claim 1 further comprising an amplifier located between said coil and said first diode for amplifying the induced signal, and a series circuit comprised of a third diode and a second resistor and connected between the output side of the amplifier and a common DC voltage source providing a relatively low voltage than that of the preceding DC source, to thereby provide a variety of control modes in accordance with the depressing speed of the key.

3. A circuit as in claim 2 wherein said amplifiers include a nected to the coil, an emitter grounded through a resistor and a collector connected to a DC source through a load and said first diode.

4. A circuit as in claim 3 wherein at least one common diode is provided to connect with each base of each of said transistors for maintaining the base voltage at a predetermined value, thereby providing the linearity of the each induced output signal responsive to the depressing speed of the respective key and temperature compensation.

5. A circuit as in claim 1 wherein each said capacitor is normally energized by said DC voltage source at a predetermined voltage to render a gating element of the keyer to be cutoff, while the voltage at the capacitor is reduced upon depression of the associated key to render said gating element to be conducting.

6. A circuit as in claim 1 wherein said direct current voltage received at said first terminal is ground.

7. A circuit as in claim 1 wherein said direct current voltage received at said first terminal is a positive voltage.

Claims

1. A tone keyer control circuit for use in an electronic musical instrument having at least a manually depressable single playing key having a magnet mounted thereon and at least a single tone keyer comprising: a coil for mounting adjacent said key so that depression of said key induces a voltage signal in said coil having an amplitude which varies with the speed with which said key is depressed, a first diode connected to said coil for receiving and rectifying said induced voltage, a capacitor connected to said first diode so as to change its voltage from an initial voltage in response to the rectified signal, an initial voltage return circuit connected to said capacitor comprising a serially connected resistor and second diode connected so that current normally flows through said capacitor via said second diode and register when said capacitor voltage is changed to return said capacitor voltage to its initial voltage, a first terminal adapted for receiving a direct current voltage, a normally open switch mounted so at to close by the depression of said key and connecting the junction between said second diode and said resistor to said first terminal, means for providing a voltage at said first terminal so that said second diode is reverse biased to prevent flow of current through said second diode, which would cause the voltage of said capacitor to return to its initial voltage, so long as said switch remains closed, and means for connecting said capacitor to said tone keyer.

3. A circuit as in claim 2 wherein said amplifiers include a plurality of transistors, each transistor having a base connected to the coil, an emitter grounded through a resistor and a collector connected to a DC source through a load and said first diode.