US3784718A

US3784718A - Touch-responsive keying circuit for electronic musical instruments

Info

Publication number: US3784718A
Application number: US00273608A
Authority: US
Inventors: Y Uchiyama
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1971-07-20
Filing date: 1972-07-20
Publication date: 1974-01-08
Anticipated expiration: 1991-01-08
Also published as: NL7210068A; CA970604A; FR2146417A1; FR2146417B1; DE2235339A1; GB1385407A; DE2235339B2; NL156259B; IT961462B; AU4464272A

Abstract

In an electronic musical instrument, tone keyer circuits are respectively controlled by touch-responsive keying circuits. The touch-responsive keying circuit comprises: a key switch having a break contact, a make contact and a movable contact; a first charge-discharge circuit having a charging capacitor and a discharging resistor both connected between the movable contact and the ground; an electrical source +B connected to the break contact; a switching transistor with its base connected to the make contact; and a second charge-discharge circuit being provided between the emitter of the transistor and the ground with a second capacitor and with a series circuit of a second resistor and an normally closed switch which is ganged with the key switch, the capacitor being connected to the keyer circuit. While the movable contact of the key switch travels from the break contact to the make contact, the first charge-discharge circuit is discharged with a predetermined time constant. The switching transistor is brought conductive to the extent responsive to a charged voltage remaining in the first chargedischarge circuit at the time the movable contact touches the make contact. The second charge-discharge circuit is charged through the transistor to establish a keying voltage.

Description

United States Patent 1191 Uchiyama Jan.8,1974

[75] Inventor:

[73] Assignee: Nippon Gakki Seizo Kabushiki Kaisha, l-lamamatsu-shi, Shizuoka-ken, Japan 22 Filed: July 20,1972

21 Appl. N01; 273,608

Yasuji Uchiyama, l-Iamakita, Japan [30] Foreign Application Priority Data July 20, 1971 Japan, 46/53580 July 20, 1971 Japan 46/63475 July 20, 1971 Japan 46/63476 [52] US. Cl 84/113, 84/126, 84/DIG. 23 [51] Int. Cl. G10h 1/02 [58] Field 01 Search 84/1.01, 1.09, 1.1,

84/113,126, 1.27, DIG. 23; 317/151; 307/108, 265; 320/1 [56] References Cited UNITED STATES PATENTS 3,535,972 10/1970 Teranishi 84/126 3,602,626 8/1971 Aramaki 84/1.01

3,626,075 12/1971 Hiyama 84/].13

3,544,699 12/1970 Harris 84/].26

3,626,074 12/1971 Hiyama... 84/1.01

3,627,897 12/1971 Harris 84/l.13 X

, 3,634,594 1/1972 Hiyama 84/l.1

3,636,232 1/1972 Hiyama 84/126 X 3,651,730 3/1972 Adachi ..84/l.26X

, Primary ExaminerRichard B. Wilkinson Assistant ExaminerStanley. J Witkowski AttorneyJohn-C. Holman et al.

[57] I ABSTRACT In an electronic musical instrument, tone keyer circuits are respectively controlled by touch-responsive keying circuits. The touch-responsive keying circuit comprises: a key switch having a break contact, a make contact and a movable contact; a first chargedischarge circuit having a charging capacitor and a discharging resistor both connected between the movable contact and the ground; an electrical source +B connected to the break contact; a switchingtransistor with its base connected to the make contact; and a second charge-discharge circuit being provided be tween the emitter of the transistor and the ground with a second capacitor and with a series circuit of a second resistor and an normally closed switch which is ganged with the key switch, the capacitor being connected to the keyer circuit. While the movable contact of the key switch travels from the break contact to the make contact, the first charge-discharge circuit is discharged with a predetermined time constant. The switching transistor is brought conductive to the extent responsive toa charged voltage remaining in the first charge-discharge circuit at the time the movable contact touches the make contact. The second chargedischarge circuit is charged through the transistor to establish a keying voltage.

5 Claims, 7 Drawing Figures Pmmmm emu 3.784.718

SHEET 10F 3 FIG. I

PRIOR ART KEYER CIRCUIT F l G. 2

PRIOR ART f1 f2 f3 TIME- Lh|+---- h2 --4 PAIENIEUJAII 8 i974 SHEEI 2 BF 3 TIME fl 12 T3 FIG. 5

TIME

PAIENTEDJAM 8 2914 SREH 3 OF 3 FIG. 6

BACKGROUND OF THE INVENTION The present invention relates generally to electronic musical instruments and more particularly to a touchresponsive keying circuit to be used in electronic musical instruments.

Conventional touch-responsive keying circuits for electronic musical instruments have been of a type as shown in FIG. 1 which comprises a key switch 1 having stationary contacts b and m and a movable contact 0. The movable contact c is connected to a first chargedischarge circuit 2 consisting of a charging capacitor C and a discharging resistor R and the break stationary contact b is connected to a D. C. source 3. The make stationary contact m is connected through a reversecurrent-blocking diode 4 to a second charge-discharge circuit 5 consisting of a charging capacitor C and a discharging resistor R An outputW for keying a keyer circuit 6 is obtained across the second chargedischarge circuit 5.

In this conventional touch-responsive keying circuit 7, as long as a key (not shown) is not depressed, the contact is maintained connected to the contact b, and therefore the capacitor C is charged through these contacts by the D.C. source 3. Under this condition, if the contact 0 is separated from the contact b at an instant t and is brought into contact with the contact m at a subsequent instant t by depressing a key, as shown in FIG. 2, the capacitor C, will be discharged through the resistor R during the period of this travelling time (from t to t In this connection, the discharge quantity in the case of a short travelling period is les than that in the case of a long travelling period. Therefore, the voltage of the capacitor C or the output keying voltage W in the case of the short travelling period (curve I) is greater in peak value than that in the case of the long travelling period (curves II and Ill). Accordingly, it will be apparent that if the key-depressing speed is controlled as desired during the playing of an electronic musical instrument, acoustic volume of the electronic musical instrument can be controlled in response to the keydepressing speed.

However, in such a circuit arrangement as described above, when the movable contact c of the switch is moved into contact with the contact m, the electrical current thereby flowing through the contacts 0 and m and the diode 4 is relatively large and, therefore, may damage the contacts of the switch 1. The damage to the contacts would be serious if the travelling time of the contacts of the switch 1 were extremely short, as the remaining voltage is high.

Furthermore, it is generally necessary for reasons of performance effect to select the time constants (C,R C R of the charge-discharge circuits so that the time period b, (FIG. 2) from an instant t when the contact 0 of the switch 1 separates from the contact b as a result of a key-depressing operation, to an instant t when the contact c comes into contact with the contact m during the same operation, is of the order of from -10 ms to 30 ms, and so that the time period h from the instant t when the contact c comes into contact with the contact m to an instant t when the contact c separates from the contact m upon release of the key is of the order of Therefore, it is necessary to select capacitors having considerably large value capacitances for these chargedischarge circuits. In addition, if the time period h, of switching the key switch 1 is made extremely long, all of the charge in the capacitor C, will be discharged through the resistor R as a result of which no output will be produced.

SUMMARY OF THE INVENTION It is accordingly a primary objectof the present invention to provide a touch-responsive keying circuit for an electronic musical instrument, in which capacitors of small capacitances can to used in charge-discharge circuits, whereby the contacts having a key switch are protected against damage by an electrical current, the above-described difficulties accompany the conventional touch-responsive keying circuit being taken into consideration.

Another object of the present invention is to provide a touch-responsive keying circuit for an electronic musical instrument, in which its output can be obtained even when the travelling time of the key switch is made longer by a soft keying operation.

A further object of the present invention is to provide a touch-responsive keying circuit for an electronic musical instrument which can ensure the production of a keying output correctly responsive to a key-depressing speed, with the output level substantially sustained during the key depression. 7

A still further object of the present invention is to provide a touch responsive keying circuit for an electronic musical instrument in which either a touchresponsive keying voltage of a level dependent on a key-depressing speed or a touch-irresponsive keying voltage of a level independent of the key-depressing speed can be selectively applied to the tone keyer circuit.

A specific object of the present invention is to provide a touch-responsive keying circuit for an electronic musical instrument in which, when a key is depressed very slowly, an output can be obtained even if a first charge and discharge circuit has been discharged, whereby a pianissimo performance effect can be easily and stably rendered as desired.

The foregoing objects and other objects of the present invention will become more apparent from the following detailed description and the appended claims when read in conjunction with the accompanying drawings, in which like parts are designated by like reference numerals and characters.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FIG. 1 is an electrical connection diagram showing a conventional touch-responsive keying circuit together with a tone keyer circuit;

FIG. 2 is a chart showing waveforms of the keying voltages for a description of the operation of the circuit shown in FIG. 1;

FIG. 3 is an electrical connection diagram showing one example of a touch-responsive keying circuit according to the present invention together with a tone keyer circuit;

FIGS. 4 and 5 are waveform charts for a description of the operation of the circuit shown in FIG. 3;

FIG. 6 is an equivalent circuit diagramof an essential part of the circuit shown in FIG. 3; and

FIG. 7 is an electrical connectiondiagram showing another example of the present invention together with a tone keyer circuit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION With reference now to FIG. 3, the example of the present invention shown therein comprises a touchresponsive keying circuit 1 1 and a tone keyer circuit 12 whose gating operation is controlled by an output W of the touch-responsive keying circuit 11. The tone keyer circuit 12 itself is a circuit well known in the art and comprises: a transistor 13 for receiving the output W of the touch-responsive keyingcircuit 11; a transistor 15 for receiving a musical tone signal I which is applied to a musical tone signal input terminal 14; and a transistor 16 for amplifying a gated output produced by the

transistors

13 and 15, whereby an output musical tone signal whose envelope is defined by the waveform of the addition to the musical tone signal I. The existence of such other combinations is indicated by the representation 18 in FIG. 3.

The movable contact 0 of a key switch 21 in the touch-responsive keying circuit 11 is connected through a resistor R to a first charge-discharge circuit 22 which comprises a charging capacitor C and a discharging resistor R and one end of the circuit 22 is connected to ground line E. Furthermore, a break contact b of the key switch 21 is connected to a power source +B (12V), and a make contact m is connected to the base of a switching transistor 23. The collector of the transistor 23 is connected to the power source +B. The emitter of the transistor 23 is connected to a charging capacitor C through a charging resistor R One terminal of the capacitor C is grounded, while the other terminal thereof is also grounded through the resistor R.,, a discharging resistor R and contacts b and c of a switch 27, which is ofa normally closed type and gang-operated with the key switch 21. Thus, a second charge-discharge circuit 28 is formed with the capacitor C and the resistors R and R The other end of the first charge-discharge circuit 22 is connected through a resistor R to the power source +B. The resistor R is a limiting resistor which serves to limit an electric current charging the capacitor C In the circuit described above, as long as an associated key is not depressed the contacts 0 of the key switches 21 and 27' are in contact with their respective break contacts b, and the capacitor C is charged through the contacts b and c of the switch 21 and the resistor R, by the power source +B. In this case, if the non-conductive and no tone signal output appears at the terminal 17.

Under this condition, when the contacts c of the

switches

21 and 27 are separated from their respective break contacts b at an instant t by a keying operation, the capacitor C begins to discharge through the resistor R As a result, a voltage V across the capacitor C decreases from about 12V with the elapse of time and with a time constant T, which is determined by the values of the capacitor C and resistor R as is indicated in FIG. 4. I

Then, under such conditions of the circuit as a decrease in the voltage of the capacitor C if the contact c of the switch 21 is brought into contact with the make contact m thereof by a quick keying operation at the instant t a relatively high voltage V remaining in the capacitor C will be applied to the base of the transistor 23 through the contacts 0 and m of the switch 21, but if the contact (3 of the switch 21 is brought into contact with the contact m thereof at another instant I, later than the instant t by a slow keying operation, a voltage.

V lower than the voltage V will be applied to the transitor 23.

Moreover, if the contact 0 of the switch 21 is brought into contact with the contact in thereof at another instant I, much later than instant t by a very slow keying operation, the capacitor C would have long been being discharged during the time period taken by the considerably slow keying operation. However, since a divided voltage which is determined by the resistor R and R is applied across the capacitor C the voltage of the capacitor C will be discharged toward that voltage, and consequently the resultant voltage of the capacitor C will never be lower than that divided voltage.

This will be apparent from the following consideration. As is shown in FIG. 6, the charge-discharge circuit 22 has a D.C. power source V,., the voltage of which is equal to Vc [R /(R -l-R X 12V, that is, a

voltage across the resistor R The DC power source V,

is connected in series to an equivalent resistance r which is composed of a parallel combination of the resistors R and R thereby forming a series circuit of r and V This series circuit is equivalent to an arrangement of parallel connection with the capacitor C Accordingly, if the instant t, is very much later, the capacitor C is discharged until the voltage thereacross becomes equal to the voltage V,, whereupon the capacitor C ceases and maintains the voltage V,.

Thus, when the voltage V V,,, or V is applied to the transistor 23, the transistor 23 becomes on or conductive at the instant t t;,, or t.,, respectively to the extent represented by the voltage V,, V or V,-. As a result, the capacitor C is charged, through the transistor 23, thus made conductive, to a voltage which is lower.

than the voltage V V; or V by a base-emitter drop voltage V and the voltage of the capacitor C thus obtained is applied, as an output W of the touch responsive keying circuit 11, to the keyer circuit 12. In this connection, because the voltage V is substantially maintained by the capacitor C the output W of a peak value which corresponds to the voltage V, is obtained for even a long time period after the instant t As long as the key is depressed and the movable contact 0 of the switch 27 is kept in contact with the make contact m, the output W is kept substantially constant, discharging very slightly through the transistor 23 only.

output W is thus produced by thecircuit 11, the

contacts c of the

switches

21 and 27 are returned into A contact with the contacts b thereof, respectively, by releasing the key, application of the charged voltage of 5 the capacitor C to the transistor 23 stops. At the same time the capacitor C is charged through the resistors R and R, by the power source +B, while the capacitor C is discharged through the resistors R and R and the switch 27. As a result, the output W of the circuit 11 is no longer produced, and the circuit 11 is restored to its original state in which no key is depressed. Consequently, the tone signal is not emitted from the terminal 17.

Thus, one cycle of the operation of the circuit 11 caused by depressing a key is accomplished; In this one cycle of operation, waveforms of the outputs W of the circuit are as shown in FIG. 5. The waveforms W W and W rise with a time constant determined mainly by the capacitance of the capacitor C and the resistance value of the resistor R at instants 2 t and t respectively, and, furthermore, undergo decay at an instant t,, with a time constant determined mainly by the capacitance of the capacitor C and the resistances of the resistors R and R The peak values of these waveforms correspond to the time periods required for switching the

key switches

21 and 27, that is, the speeds of the key-depressing operations.

Another example of the present invention as illustrated in FIG. .7 has a touch-responsive keying circuit 11 further comprising a change-over switch 25 provided with switching contactsj and k. The contactj is connected to the contact b ofa key switch 21, while the contact k is connected to the contact c of the key switch 21 through a resistor 26 and a diode 27 as required. Furthermore, a movable contact I is connected to a power source +8. The diode 27 serves to block a reverse current in the case when a plurality of touchresponsive keying circuits are switched over by using one common change-over switch 25. The other components and their-arrangements are the same as those described with reference to FIG. 3.

In the circuit described above, a touch-responsive output of the circuit 11 can be obtained by connecting the movable contact I to the contact j. The other general operations of the circuit are the same as those described with reference to FIG. 3.

When a touch-irresponsive output is to be produced from the circuit 11, the movable contact I is moved into contact with the contact k. Under this condition, when the contacts 0 of the

switches

21 and 27 are brought into contact with their respective contacts m by a keying operation, i.e., by a depressing the key, predetermined voltage is applied to the base of the transistor 23 by the power source +B through the movable contact 1, the contact k, the resistor 26, the diode 27 and the contacts c and m of the switch 21.

As a result, the capacitor C is charged to a voltage corresponding to the predetermined voltage, and the voltage of the capacitor C thus obtained becomes a touch-irresponsive output W of the circuit. In this connection, the predetermined voltage is determined by the resistors 26, R and R diode 27, and power source +B.

Thus, the keyer circuit l2 produces a musical tone signal having an envelope of a certain level keyed by the constant output W. This operation of the circuit 12 is the same as the ordinary operation of a conventional tone keyer circuit, having no touch-responsive circuit, of an electronic musical instrument.

As is described above, according to the present invention, both the touch-responsive output which causes the keyer circuit to produce a musical tone sig nal having an envelope of a level determined by the keying speed and the touchirresponsive output which causes the keyercircuit to produce a musical tone signal having an envelope of a predetermined level regardless of the keying speed can be selectively obtained immediately by merely changing-over the switch 25 without troublesome operations.

In addition, even in the case when the keying operation is conducted quickly or slowly as desired in order to obtain the touch-responsive output, the touchresponsive output can be obtained. For this purpose, since the rising time and decay time of the touchresponsive output are caused to be of a small value of the order of 50ms, the values of the capacitors of the charge-discharge circuits can be made considerably small.

Furthermore, while an example wherein the movable contact I of the change-over switch 25 is connected to v a common and fixed power source +B has been described above, it is also possible to connect the movable contact I to a voltage adjustable power source proj vided separately such as shown by dotted lines in FIG. 7 and then to selectively set the level of the touchresponsive output W or the level of the touchirresponsive output W by adjusting the voltage of the adjustable power source.

Only one touch-responsive. keying circuit 11 is shown in the accompanying drawings, but in practice a plurality of touch-responsive keying circuits are provided. In

this case, one changeover switch 25 may be provided in common for those plurality of touch-responsive keying circuits, so that the contactsj and k of the switch 25 are connected to the contact b of the switch 21 and the resistor 26 in each touch-responsive keying circuit.

1 claim: 1. A touch-responsive keying circuit comprising: a

circuit ground; a power source; a key switch having a break contact connected to said power source, a make contact and a movable contact; a first charge-discharge circuit having a charging capacitor and a discharging resistor both connected between said movable contact and said ground; a transistor having a base connected to said make contact, a collector connected to said power source, and an emitter; and a second chargedischarge circuit including a second capacitor connected between said emitter and said ground, a second resistor and a second switch connected in series between said emitter and said ground, said second switch being of a normally closed type and gang-operated with said key switch.

2. A touch-responsive keying circuit as claimed in claim 1, in which said first charge-discharge circuit is provided with means for applying across said charging capacitor a divided voltage of said power source, whereby when the first charge-discharge circuit is discharged, the resultant voltage of the first charge and discharge circuit is maintained not lower than said divided voltage.

3. A touch-responsive keying circuit as claimed in claim 1 which further comprises a change-over switch having a first stationary contact connected to said power source.

5. A touch-responsive keying circuitas claimed in claim 3, in which a plurality of touch-responsive keying circuits are provided, and one common change-over switch is provided for these touch-responsive keying circuits.

Claims

1. A touch-responsive keying circuit comprising: a circuit ground; a power source; a key switch having a break contact connected to said power source, a make contact and a movable contact; a first charge-discharge circuit having a charging capacitor and a discharging resistor both connected between said movable contact and said ground; a transistor having a base connected to said make contact, a collector connected to said power source, and an emitter; and a second charge-discharge circuit including a second capacitor connected between said emitter and said ground, a second resistor and a second switch connected in series between said emitter and said ground, said second switch being of a normally closed type and gang-operated with said key switch.

3. A touch-responsive keying circuit as claimed in claim 1 which further comprises a change-over switch having a first stationary contact connected to said charge-discharge circuit, a second stationary switching contact connected to the break contact of said key switch, and a movable contact connected to said power source.

4. A touch-responsive keying circuit as claimed in claim 3 in which a movable contact of said change-over switch is connected to a separately provided adjustable power source.

5. A touch-responsive keying circuit as claimed in claim 3, in which a plurality of touch-responsive keying circuits are provided, and one common change-over switch is provided for these touch-responsive keying circuits.