SIGNAL-SELECTING SYSTEM FOR A KEYBOARD TYPE ELECTRONIC MUSICAL INSTRUMENT
United States Patent 3836692
A signal-selecting system for a keyboard type electronic musical instrument comprising keyswitches, memory means, tone signal sources, signal-switching means, frequency dividers, key-selecting means, octave-selecting means, detecting means and a power source. By employing memory means and tone signal sources corresponding to the notes of one octave, a signal selecting operation for several octaves can be carried out by detecting the extreme keyswitch group and detecting the extreme keyswitch in each of the keyswitch groups even when a plurality of keyswitches corresponding to several octaves are closed simultaneously. The tone signals which do not correspond to the provided tone signal sources are provided by dividing the frequency of the corresponding original octave by a factor of two in each divider.
US Patent References:
ELECTRONIC LATCH AND WIPEOUT SYSTEM FOR MUSICAL INSTRUMENTS
Munch, Jr. et al. - November 1970 - 3542935
CONTROLED SWITCHING OF OCTAVES IN AN ELECTRONIC MUSICAL INSTRUMENT
Yamashita - August 1971 - 3598892
MONOPHONIC ELECTRONIC MUSICAL INSTRUMENT WITH A VARIABLE FREQUENCY OSCILLATOR EMPLOYING POSITIVE FEED BACK
Adachi - April 1972 - 3659031
PLURAL TONE SELECTOR FOR AN ELECTRONIC MUSICAL INSTRUMENT
Suzuki - June 1972 - 3671659
ELECTRONIC LATCH AND WIPEOUT SYSTEM FOR MUSICAL INSTRUMENTS
Munch, Jr. et al. - November 1970 - 3542935
CONTROLED SWITCHING OF OCTAVES IN AN ELECTRONIC MUSICAL INSTRUMENT
Yamashita - August 1971 - 3598892
MONOPHONIC ELECTRONIC MUSICAL INSTRUMENT WITH A VARIABLE FREQUENCY OSCILLATOR EMPLOYING POSITIVE FEED BACK
Adachi - April 1972 - 3659031
PLURAL TONE SELECTOR FOR AN ELECTRONIC MUSICAL INSTRUMENT
Suzuki - June 1972 - 3671659
Application Number:
05/300256
Publication Date:
09/17/1974
Filing Date:
10/24/1972
View Patent Images:
Export Citation:
Assignee:
Matsushita Electric Industrial Co., Ltd. (Osaka, JA)
Primary Class:
Other Classes:
84/675, 984/339
International Classes:
G10H1/22; G10K1/00
Field of Search:
84/1.01,1.17,DIG.2,DIG.20
Primary Examiner:
Wilkinson, Richard B.
Assistant Examiner:
Weldon U.
Attorney, Agent or Firm:
Wenderoth, Lind & Ponack
Claims:
What is claimed is
1. A signal selecting system for a keyboard type electronic musical instrument, comprising:
2. memory means corresponding to the 12 notes of one octave and coupled through said preference circuit means to corresponding keyswitches for the same notes in the respective groups;
3. tone signal sources for generating tone signals corresponding to said 12 notes of one octave;
4. signal switching means connected between said 12 memory means and the corresponding 12 tone signal sources for switching on a tone signal source upon the operation of the corresponding memory means, said preference circuit means coupled to said memory means for switching on and setting the memory corresponding to the keyswitch which is closed;
5. A signal selecting system as claimed in claim 1, wherein said first detecting means comprises at least two detectors coupled between corresponding octave-groups of keyswitches and said further memory means for detecting the closure of any keyswitch thereof and then inhibiting the operation of the less extreme octave-groups.
6. A signal-selecting system as claimed in claim 1 wherein said 12 memory means comprise flip-flop circuits.
7. A signal-selecting system as claimed in claim 1 wherein said further memory means comprises flip-flop circuits.
8. A signal-selecting system as claimed in claim 1 wherein said frequency dividers each comprise a flip-flop circuit.
1. A signal selecting system for a keyboard type electronic musical instrument, comprising:
2. memory means corresponding to the 12 notes of one octave and coupled through said preference circuit means to corresponding keyswitches for the same notes in the respective groups;
3. tone signal sources for generating tone signals corresponding to said 12 notes of one octave;
4. signal switching means connected between said 12 memory means and the corresponding 12 tone signal sources for switching on a tone signal source upon the operation of the corresponding memory means, said preference circuit means coupled to said memory means for switching on and setting the memory corresponding to the keyswitch which is closed;
5. A signal selecting system as claimed in claim 1, wherein said first detecting means comprises at least two detectors coupled between corresponding octave-groups of keyswitches and said further memory means for detecting the closure of any keyswitch thereof and then inhibiting the operation of the less extreme octave-groups.
6. A signal-selecting system as claimed in claim 1 wherein said 12 memory means comprise flip-flop circuits.
7. A signal-selecting system as claimed in claim 1 wherein said further memory means comprises flip-flop circuits.
8. A signal-selecting system as claimed in claim 1 wherein said frequency dividers each comprise a flip-flop circuit.
Description:
FIELD OF THE INVENTION
This invention relates to a keyboard type electronic musical instrument, and more particularly to a novel and improved signal-selecting system which is capable of selecting the tone signal having the highest or the lowest frequency from among tone signals produced by keys which are depressed simultaneously.
DESCRIPTION OF THE PRIOR ART
A conventional keyboard type electronic musical instrument is provided with a conventional signal-selecting system comprising many transfer type keyswitches, each of which has a break-contact, a make-contact and a movable-contact. Transfer type keyswitches are connected in such a way that the make-contacts of the transfer type keyswitches are connected to set terminals of memory means, each respectively, and connected in series in such a way that the movable-contact of one transfer type keyswitch is connected to the break-contact of another transfer type keyswitch. The movable-contact of said another transfer type keyswitch is connected to the break contact of a further transfer type keyswitch, and so on.
Said memory means comprise, for example, flip-flop circuits which employ two transistors respectively and control switching-on and switching-off of tone signals from corresponding tone generators.
However, the conventional signal-selecting system has the disadvantage that as many memory means are required as there are keyswitches, and when a flip-flop circuit is used for the memory means, many transistors are required, especially for an instrument having keyswitches for several octaves.
Further, because the many keyswitches for several octaves are connected in series, it becomes necessary that these keyswitches have a very high reliability so as to present defective operation such as frequent break-down due to poor contacts of the keyswitches.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel and improved signal-selecting system for a keyboard type electronic musical instrument.
Another object of the present invention is to provide a compact and reliable signal-selecting system comprising a plurality of keyswitches corresponding to several octaves and twelve memory means corresponding to one octave.
A further object of the present invention is to provide an improved signal-selecting system comprising tone generators corresponding to one octave and more than one frequency divider, and which is capable of providing the selected tone signal having the lowest frequency from among the tone signals corresponding to several octaves when a plurality of keyswitches are depressed simultaneously.
A still further object of the present invention is to provide an improved signal-selecting system comprising tone generators corresponding to one octave and more than one frequency multiplier, and which is capable of providing the selected tone signal having the highest frequency from among the tone signals corresponding to several octaves when a plurality of keyswitches are depressed simultaneously.
A further object of the present invention is to provide an improved signal-selecting system comprising a plurality of keyswitches corresponding to several octaves and an octave-selecting means for detecting the keyswitch group corresponding to the highest or lowest octave.
These objects are achieved by employing a signal-selecting system according to the present invention which comprises a plurality of keyswitches which are actuated by corresponding keys of a keyboard, said keyswitches being in a range of more than two octaves and being divided into a number of keyswitch groups equal to the number of octaves;;
a memory circuit having a plurality of memory means corresponding to the notes of one octave;
a plurality of tone signal sources for generating the tone signals corresponding to the notes of one octave;
a plurality of signal-switching means corresponding to the notes of one octave, each of said signal-switching means being connected between the corresponding memory means and the corresponding tone signal source respectively, said switching means switching a selected tone signal according to the operation of said memory means;
one or a plurality of frequency dividers connected in series, said frequency dividers dividing the frequency of the tone signal applied thereto by a factor of two;
key-selecting means for selecting the extreme keyswitch of the keyswitches which are closed simultaneously in each of said keyswitch group and supplying electric power to the corresponding memory means so as to set it, keyswitches which are in different keyswitch groups and in one or more than one octave relation to each other being connected in common;
an octave-selecting means for detecting the extreme group of the keyswitch groups containing the keyswitches which are closed simultaneously and then switching off the supply of electric power to the keyswitch groups keyswitches of which are set in the opposite direction from the key switches in said detected extreme keyswitch group, said octave-selecting means selecting the number of said frequency dividers to be operated by applying the switched tone signal directly to the first one of said frequency dividers so that the frequency of said switched tone signal is divided in turn by all of said frequency dividers connected in series or by bypassing some of said frequency dividers so that the frequency of said switched tone signal is divided in turn by the rest of the frequency dividers, the divided frequency of the tone signal provided at an output terminal of the signal-selecting system corresponding to the extreme keyswitch of the keyswitches which are closed simultaneously in the whole range;
a detecting means for detecting the moment when another extreme keyswitch of said plurality of keyswitches is closed and then for generating a reset pulse for resetting the memory means which has been set previously; and
a power source which is connected through said octave selecting means and said detecting means, respectively to each of said keyswitch groups.
BRIEF DESCRIPTION OF THE DRAWINGS
These objects and other features of the present invention will be made clear from the following detailed description of the invention considered together with the accompanying drawings wherein:
FIG. 1 is a schematic circuit diagram for explaining a signal selecting operation of a signal-selecting system for a keyboard type-electronic musical instrument according to the present invention.
FIG. 2 is a circuit diagram, of an example of memory means and detecting means shown in FIG. 1.
FIG. 3 is a schematic circuit diagram of a signal-selecting system for a keyboard type electronic musical instrument according to the present invention.
FIG. 4 is a circuit diagram of an embodiment of the signal-selecting system of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The signal-selecting system of the invention will be described, for convenience, as using transfer type keyswitches connected in series as the key-selecting means. However, the present invention can make use of substantially any kind of key-selecting means which is capable of producing voltage at an output terminal corresponding to the extreme key depressed simultaneously. For example, the present invention can use as a key-selecting means the selecting circuit which is disclosed in U.S. Pat. No. 3,585,892 of the same applicant which comprises a totem-pole connection of transistors, each base being connected to a corresponding keyswitch. Therefore, the present invention is not restricted to a key-selecting means which uses transfer type keyswitches connected in series.
Referring to FIG. 1, there will be described the general operation of a signal-selecting system for a keyboard type electronic musical instrument. A plurality of keyswitches K 1 , K 2 , K 3 . . . , K n are connected to corresponding keys of the electronic musical instrument, respectively. The break-contacts of the keyswitches are connected in series to the movable-contacts of the subsequent keyswitches, each respectively, as shown in FIG. 1. That is, the break-contact of the keyswitch K 1 is connected to the movable-contact of the next keyswitch K 2 , and so on. The make-contacts of the keyswitches are connected to a corresponding memory means in a memory circuit 1, and the movable-contact of the keyswitch K 1 is connected to a power source through a detecting means 22 and a terminal 21. Therefore, even when a plurality of the keyswitches, for example the keyswitches K 1 and K 2 , are closed simultaneously, the electric power is only applied to the memory means corresponding to the keyswitch K 1 because the movable-contact of the keyswitch K 2 is connected to the break-contact of the keyswitch K 1 and so the keyswitch K 2 is not connected to the terminal 21.
The memory circuit 1 contains as many memory means as there are keyswitches K 1 , K 2 , K 3 , . . . , K n , and each of the memory means is connected to the corresponding keyswitch, respectively. A flip-flop circuit employing two transistors may be used for the memory means.
Further, a plurality of tone signal sources 2 equal in number to the number of the keyswitches K 1 , K 2 , K 3 , . . . , K n are connected to the corresponding memory means, respectively. The switching-on and off of the tone signal from the tone signal source is controlled by the memory means, e.g., according to change of the operating condition of the flip-flop circuit. Then, the tone signal is provided to an output terminal 20 through the memory circuit 1.
A D.C. voltage is applied at the terminal 21 as a power source for the system. Further, the operating condition of the flip-flop circuit of the memory circuit 1 is changed through the detecting means 22 by the electric power applied to the terminal 21. The detecting means detects each time when any of the movable-contacts of the keyswitches is closed against a make-contact or when more than two of the memory means are set simultaneously, and resets all the flip-flop circuits of the memory circuit 1. Then, a flip-flop circuit is set corresponding to the keyswitch for the lowest or highest frequency. Such a signal selecting operation is described in more detail in the following.
Referring to FIG. 2 which is an example of a circuit configuration corresponding to the schematic diagram of FIG. 1, the same parts as those in FIG. 1 are designated by the same reference numerals and the memory circuit 1 is formed of a plurality of flip-flop circuits, each comprising two transistors T 1 and T 2 and resistors R 1 and R 2 , T 3 and T 4 and identical resistors R 1 and R 2 , and so on. Resistors R 3 and R 4 are connected in series with resistors R 1 and ground. Signal-switching means are provided comprised of diodes D 1 , D 2 , . . . , and each of them is connected between the corresponding tone generator S 1 , S 2 . . . , and output terminal 20 through a junction between resistors R 3 and R 4 . Resistor R 5 is connected between the junction between resistors R 1 , R 2 and the collector of transistor T 1 , T 2 . . . , and the junction between the tone generator and the diode. For simplicity, the signal-switching means is shown in combination with the memory circuit in FIGS. 1 to 4. The detecting means 22 in FIGS. 2 and 4 is composed of three switching amplifiers, a differentiator and a rectifier. These are connected as follows. One switching amplifier is composed of a transistor T 11 , the emitter of which is connected to the electric power source through a terminal 21 for the detecting means power supply, the collector of which is connected through a collector resistor R 11 to ground, and the base of which is supplied with ground potential when all of the keyswitches are closed. The differentiator is composed of a capacitor C 1 , one end of which is connected to the collector of the transistor T 11 and resistor R 12 , which is connected between ground and the other end of the capacitor C 1 . The rectifier is composed of a diode D 11 , which is connected in parallel with the resistor R 12 and the anode of which is connected to ground. The second switching amplifier is composed of a transistor T 12 , the emitter of which is connected to ground, the collector of which is connected through a collector resistor R 13 and the terminal 21 to the electric power source, and the base of which is connected to the cathode of the diode D 11 . The third switching amplifier is composed of a transistor T 13 , the emitter of which is connected to ground, the collector of which is connected through a collector resistor R 14 and the terminal 21 to the electric power source, and the base of which is connected to the collector of the transistor T 12 .
The transistors T 11 and T 12 are normally switched off and the transistor T 13 is normally switched on when none of the keyswitches are closed. The differentiator differentiates the voltage change at the collector of the transistor T 11 . The rectifier rectifies the output of the differentiator and produces a positive going trigger pulse. The switching amplifiers with transistors T 12 and T 13 amplify and shape the input trigger pulse so as to produce a positive going rectangular pulse which resets the flip-flop circuits in the memory means 1. When the keyswitch K 1 is closed by depressing the corresponding key, a current flows to the transistor T 1 through a resistor R 8 and the transistor T 1 is saturated.
On the other hand, a transistor T 11 in the detecting means 22 is also saturated because the current flowing to the transistor T 1 at closing of the keyswitch K 1 becomes the base current of the transistor T 11 . By differentiating this instant current with a capacitor C 1 , a positive pulse is provided at the base of a transistor T 12 , and thereby the transistor T 12 is saturated and a transistor T 13 is cut off.
The collector of the transistor T 13 is connected through resistors R 7 to the base of each transistor T 2 , T 4 , . . . , of the flip-flop circuits, respectively. Therefore, when the transistor T 13 is cut off, base current flows to the transistors T 2 , T 4 , . . . through a resistor R 14 . Then, the transistors T 2 , T 4 , . . . , are saturated, and this state is maintained.
However, in the flip-flop circuit comprising the transistors T 1 and T 2 , because the transistor T 1 is saturated, as described above, by the closed keyswitch K 1 , the transistor T 2 is cut off when the positive pulse disappears, and this state is held even after the keyswitch K 1 is opened.
Resistance values of resistors R 1 , R 2 , R 3 and R 4 of the flip-flop circuit have values in the relation of the following equation:
R 2 /R 1 + R 2 > R 4 / R 3 + R 4 > 0.
When the transistor T 1 is saturated, the diode D 1 is conductive, and accordingly a tone signal S 1 corresponding to the keyswitch K 1 is provided to the output terminal 20. On the other hand, the diode D 2 in the second memory means is cut off because the transistor T 3 is cut off and because of the above relation, R 2 / R 1 + R 2 > R 4 / R 3 + R 4 , so that other tone signals S 2 , S 3 . . . are not supplied to the output terminal 20. Consequently, there is provided a signal switching operation for the selected tone signal.
Then, when another keyswitch K 2 is closed, with a voltage applied to the terminal 21, a current flows to the transistor T 3 through the transistor T 11 of the detecting means 22, the keyswitches K 1 and K 2 and the resistor R 8 , and the transistor T 3 is saturated. As in the case of keyswitch K 1 instant of closing the keyswitch K 2 is detected by the transistor T 11 , and the transistor T 13 is cut off through the transistor T 12 , so that the transistors T 2 , T 4 , . . . are saturated through the resistors R 7 , respectively and this state is held. At saturation of the transistor T 2 , the transistor T 1 , and so also the diode D 1 are cut off, and accordingly the tone signal S 1 is not supplied to the output terminal 20. On the other hand, the transistor T 3 is saturated due to the closing of the keyswitch K 2 , so that the diode D 2 is conductive and the other diodes are cut off in the same manner as described above. Accordingly, only the tone signal S 2 corresponding to the keyswitch K 2 is selectively supplied to the output terminal 20.
There has been described hereinbefore the fundamental signal selecting operation for a keyboard type electronic musical instrument, and the operation of the signal selecting system of the invention is also similar to the above. However, according to the present invention, the signal selecting operation for a plurality of keyswitches corresponding to several octaves can be provided by employing only the memory means and the tone generators corresponding to one octave. Such a novel and improved signal selecting system will now be described.
Referring to FIG. 3 which shows a schematic diagram of the signal selecting system of the present invention, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and the system is shown for an instrument having keys corresponding to three octaves.
A plurality of keyswitches K 1 , K 2 , . . . , K 26 , K 27 are divided into three keyswitch groups, groups 31 for K 1 to K 12 , group 32 for K 13 to K 24 and group 33 for K 25 to K 36 , corresponding to the respective octaves. In each of the keyswitch groups, each of the break-contacts of the keyswitches is connected to the movable-contact of the subsequent keyswitch, respectively, so as to carry out the signal selecting operation when a plurality of keyswitches are depressed simultaneously, as described hereinbefore referring to FIG. 1. On the other hand, the make-contacts of the keyswitches which are in an octave relation, i.e., the keyswitches K 1 , K 13 and K 25 , and K 2 , K 14 and K 26 and so on, are connected in common, respectively.
The memory circuit 1 is one similar to that of FIG. 1, and it has as many memory means as the number of tones corresponding to one octave, i.e., 12 memory means, each of which consists of a conventional flip-flop circuit, for example. Tone signal sources 2 are also similar to those of FIG. 1 and they provide the tone signals for one octave. Each of the tone signal sources 2 is connected to the corresponding one of the 12 flip-flop circuits, respectively, and the switching on and off of the tone signal is controlled according to the condition of the flip-flop circuits.
The frequency of the tone signal provided to the terminal 20 through the memory circuit 1 is divided by frequency dividers 3 and 4 by a factor of two, respectively. By means of an octave-selecting means 5, the tone signal is applied to the frequency divider 4 through the other frequency divider 3 or directly through a gate circuit 13 instead of through the divider 3.
The octave-selecting means 5 contains three detectors 6, 7 and 8 which are coupled to the respective keyswitch groups in such a way that the detector 6 is operated when a keyswitch in the first keyswitch group 31 of K 1 to K 12 is closed, the detector 7 is operated when a keyswitch of the second group 32 is closed, and the detector 8 is operated when a keyswitch of the third keyswitch group 33 of K 25 , K 26 , . . . , K 36 is closed.
The octave-selecting means 5 further contains two memory circuits 11 and 12 which have set terminals connected to the detectors 7 and 8, respectively, and memory circuit 11 has a reset terminal connected to detector 6 and memory circuit 12 has a reset terminal connected to detectors 7 and 8, so that the memory circuit 11 is set by a pulse provided from the detector 7 and reset by a pulse provided from the detector 6, and the memory circuit 12 is set by a pulse from the detector 8 and reset by pulses from the detectors 6 and 7. When the memory circuit 11 is set, the gate circuit 13, which is connected thereto, is conductive and the tone signal provided to the terminal 20 is directly applied to the frequency divider 4 jumping the other frequency divider 3. Then, the tone signal divided by the frequency divider 4 is provided to an output terminal 23. In this case, the frequency of the tone signal provided at the output terminal 23 is a half that of the tone signal provided at the terminal 20.
There is further provided another gate circuit 14 which bypasses gate circuit 13 and frequency divider 4, and which is connected to the memory circuit 12 and is conductive when memory circuit 12 is set and which provides the tone signal at the terminal 20 directly to the output terminal 3 without passing through the frequency dividers 3 and 4. Therefore, the frequency of the tone signal provided at the output terminal 23 is the same as that of the tone signal provided at the terminal 20. When neither of the gate circuits 13 and 14 are conductive, the tone signal provided at the terminal 20 is applied to the frequency divider 3, and the output signal therefrom is further applied to the other frequency divider 4. Therefore, in this case, the tone signal provided to the output terminal 23 has a frequency which is a quarter of that of the tone signal provided to the terminal 20.
The octave-selecting means 5 further contains two switching circuits 9 and 10 connected between keyswitch group 32 and detector 7 and between keyswitch group 33 and detector 8, respectively, and which are normally condutive. The switching circuit 9 is connected to the detector 6 through a diode D 12 and it is cut off on the operation of the detector 6. The switching circuit 10 is connected to the detectors 6 and 7 through diodes D 13 and D 14 , respectively, and it is cut off on the operation of the detector 6 or 7.
The detecting means 22 is similar to that of FIG. 1. Upon detecting the instant when the keyswitches are closed, the detecting means 22 resets all of the flip-flop circuits of the memory circuit 1, and thereby always only one tone signal is selectively provided to the terminal 20. The operation of the detecting means 22 is described in detail hereinbefore in connection with FIG. 2. In the following, there will be described in more detail the operation of the signal selecting system shown in FIG. 3.
Referring to FIG. 4 which shows a circuit configuration of an embodiment of the signal selecting system of the invention, the same parts as those of FIG. 3 are designated by the same reference numerals. The memory circuit 1 and the tone generators 2 are shown in a block, respectively because an example of practical circuit configurations thereof are shown in FIG. 2. However, the number of the memory means and the tone generators present of course correspond to the notes of one octave, i.e., only 12, respectively,
In FIG. 4, a flip-flop circuit is employed for each of the frequency dividers 3 and 4. The frequency divider 3 divides the frequency of the tone signal by a factor of two, and the frequency divider 4 divides the frequency of the tone signal provided from the frequency divider 3 by a factor of two.
The detectors 6, 7 and 8 comprise transistors T 15 , T 16 and T 17 and grounded resistors R 15 , R 16 and R 17 connected to the collectors, respectively. Resistors r 16 and r 17 are connected across the base and emitter of transistors 16 and 17, respectively. When the keyswitches of the keyswitch groups 31 (K 1 , K 2 , . . . , K 12 ), , 32 (K 13 , K 14 , . . . , K 24 ) AND 33 (K 25 , K 26 , . . . , K 36 ) are closed, respectively, the transistors T 15 , T 16 and T 17 are saturated, respectively, and it is thus detected that the keyswitches of each of the keyswitch groups are closed.
The memory circuits 11 and 12 also comprise flip-flop circuits consisting of transistor T 21 and T 22 , and T 23 and T 24 , respectively. The memory circuit 11 is set through a diode D 16 when a positive voltage is provided at the collector of the transistor T 16 of the detector 7, and it is reset through a diode D 15 when a positive voltage is provided at the collector of the transistor T 15 of the detector 6. The memory circuit 12 is set through a diode D 19 when a positive voltage is provided at the collector of the transistor T 17 of the detector 8, and it is reset through diode D 17 or D 18 when a positive voltage is provided at the collector of the transistor T 15 or T 16 of the detector 6 or 7, respectively.
The anode of a diode D 22 forming part of the gate circuit 13 is connected to the collector of the transistor T 21 of the memory circuit 11 through a resistor R 26 , and the cathode of the diode D 22 is connected to the terminal 20. Therefore, when the transistor T 21 of the memory circuit 11 is cut off, the diode D 22 is conductive and by-passes the frequency divider 3, so that the tone signal provided at the terminal 20 is applied to the second frequency divider 4. When the transistor T 21 of the memory circuit 11 is saturated, the diode D 22 is not conductive.
Similarly, a diode D 21 forming part of the gate circuit 14 is connected to the collector of transistor T 23 of memory circuit 12 and is conductive when the transistor T 23 of the memory circuit 12 is cut off and gate circuit 14 thus by-passes the frequency dividers 3 and 4, so that the tone signal provided at the terminal 20 to which the cathode of diode D 21 is connected is directly applied to the output terminal 23. When the transistor T 23 of the memory circuit 12 is saturated, the diode D 22 is cut off.
The frequency dividers 3 and 4 are arranged to be triggered by a negative pulse. A capacitor C 4 differentiates the fall of the tone signal and provides a negative pulse to trigger the frequency divider. A negative pulse having the tone signal frequency is provided at the output terminal 23.
Accordingly, even when the frequency of the tone signal provided at the terminal 20 is not varied, the tone signal provided at the output terminal 23 has in relation to the frequency of the tone signal at terminal 20, a frequency lower by two octaves when neither of the gate circuits 13 and 14 are conductive, a frequency lower by one octave when only the gate circuit 13 is conductive and the same frequency when the gate circuit 14 is conductive.
The switching circuits 9 and 10 comprise transistors T 18 and T 19 and resistors R 18 and R 19 connected to the bases thereof, respectively. Normally, both of the switching circuits 9 and 10 are conductive due to the base current flowing through the resistors R 18 and R 19 , respectively. At this time, the base currents of the transistors T 18 and T 19 become the base currents of the transistors T 16 and T 17 of the detectors 7 and 8, respectively. However, the resistance values of the resistors R 18 and R 19 are made sufficiently large and the base current is shunted by resistors r 16 and r 17 , respectively, so that the transistors T 16 and T 17 of the detectors 7 and 8 are not saturated.
When the transistor T 15 of the detector 6 is saturated, the base current of the transistor T 18 in the switching circuit 9 flows through the resistor R 18 from the collector of the transistor T 15 through the diode D 12 , and so the transistor T 18 is cut off. Accordingly, electric power is not provided to the second keyswitch group K 13 , K 14 . . . , K 24 . Similarly, the switching circuit 10 is cut off when the detector 6 or 7 is operated, and so electric power is not provided to the third keyswitch group K 25 , K 26 , . . . , K 36 .
The detecting means 22 is similar to that of FIG. 2. Upon detecting the instant key when the keyswitches are closed, the detecting means 22 resets all of the flip-flop circuits of the memory circuit 1, and thereby only one tone signal is selectively provided to the terminal 20.
As described hereinbefore, it will be understood that the octave-selecting means, which comprises the detectors 6, 7 and 8, the switching circuits 9 and 10, the memory circuits 11 and 12, and the gate circuits 13 and 14, detects the keyswitch groups containing the keyswitches which are closed and selects the extreme keyswitch group corresponding to the lowest or highest tone in these keyswitch groups, and then it stops providing electric power to all the keyswitch groups for tones above or below, as the case may be, the selected extreme keyswitch group. Further, at the same time, the octave-selecting means sets the frequency dividers so as to provide the tone signal having the frequency corresponding to the extreme key for the lowest or highest tone signal among the keys on the same keyboard which are depressed simultaneously.
Because the keyswitches are connected in series, as described hereinbefore, in each of the keyswitch groups, it is clear that a signal selecting operation is provided for each of the keyswitch groups. For example, in the first keyswitch group of K 1 , K 2 , . . . , K 12 , the signal selecting operation is described in connection with FIG. 1. Hereinafter there will be described in detail the signal selecting operation between the keyswitch groups.
When the keyswitch K 25 is closed, for example, a voltage applied to the terminal 21 is supplied to one flip-flop circuit of the memory circuit 1 corresponding to the keyswitches K 1 , K 13 and K 25 through the detecting means 22, the detector 8, the switching circuit 10 and the keyswitch K 25 , and said one flip-flop circuit is set. Therefore, a tone signal corresponding to the tone for keyswitch K 25 , but which can be divided to produce tones corresponding to keyswitches K 13 and K 1 , is terminal 20.
On the other hand, by the operation of the detector 8, the memory circuit 12 is set, and then the gate circuit 14 is made conductive. Therefore, the tone signal at the terminal 20 is supplied to the output terminal 23 as it is.
When the keyswitches K 13 and K 25 are closed simultaneously, one flip-flop circuit corresponding to the keyswitches K 1 , K 13 and K 25 is again set through the detector 7, the switching circuit 9 and the keyswitch K 13 . On the other hand, the switching circuit 10 is cut off by the operation of the detector 7, so that the detector 8 is not operated. Further, by the operation of the detector 7, the memory circuit 12 is reset and the memory circuit 11 is set. Consequently, the gate circuit 14 is closed and the gate circuit 13 is made conductive. Accordingly, the frequency of the tone signal at the terminal 20 is divided by the frequency divider 4 and the tone signal having a frequency of a half of that of the signal at the terminal 20 is provided to the output terminal 23.
When the keyswitches K 1 , K 13 and K 25 are closed simultaneously, one flip-flop circuit corresponding to these keyswitches is set through the detector 6 and the keyswitch K 1 , and the corresponding tone signal is switched on. On the other hand, by the operation of the detector 6, the switching circuits 9 and 10 are cut off, and so there is no current flowing to the detectors 7 and 8. Consequently, the memory circuits 11 and 12 are reset, and so the gate circuits 13 and 14 are cut off. Accordingly, the frequency of the tone signal at the terminal 20 is divided by the frequency dividers 3 and 4 by a factor of two, respectively so that there is provided a tone signal having a frequncy one quarter of that of the signal at the terminal 20 at the output terminal 23.
As described above, even when a plurality of keyswitches are closed simulaneously, always only the lowest tone signal is provided preferentially. It is of course possible to provide preferentially the highest tone by modifying slightly the manner of triggering of the switching circuits 9 and 10 and the gate circuits 13 and 14 of the system described above.
As described hereinbefore, according to the present invention, by employing the memory means and tone generators corresponding to the notes of one octave, a signal selecting operation can be performed for the keyswitches corresponding to the notes of several octaves. Therefore, there are the great advantages that the number of electronic components for the signal selecting system can be reduced, that because the number of the keyswitches which are to be connected in series can be reduced when transfer type keyswitches are used, the troubles due to poor contact of the keyswitches can be greatly reduced and a high reliability is obtained even when using the usual inexpensive transfer type keyswitches which are not so high in quality, and further that manufacturing steps can be reduced because of a reduced number of wiring connections in the keyswitches, and so on.
While a particular embodiment of the invention has been described hereinbefore, it will be apparent that various modifications can be made in the form and construction thereof. For example, other circuit besides the flip-flop circuit may be used for the memory means of the memory circuit, the frequency dividers and the memory circuit of the octave-selecting means. The same is true with respect to the signal-switching device, the switching circuit, and the detector. Moreover, there has been described above the modification in which the system selects the highest frequency tone signal wheras the parts can be easily modified to select the lowest frequency tone signal.
This invention relates to a keyboard type electronic musical instrument, and more particularly to a novel and improved signal-selecting system which is capable of selecting the tone signal having the highest or the lowest frequency from among tone signals produced by keys which are depressed simultaneously.
DESCRIPTION OF THE PRIOR ART
A conventional keyboard type electronic musical instrument is provided with a conventional signal-selecting system comprising many transfer type keyswitches, each of which has a break-contact, a make-contact and a movable-contact. Transfer type keyswitches are connected in such a way that the make-contacts of the transfer type keyswitches are connected to set terminals of memory means, each respectively, and connected in series in such a way that the movable-contact of one transfer type keyswitch is connected to the break-contact of another transfer type keyswitch. The movable-contact of said another transfer type keyswitch is connected to the break contact of a further transfer type keyswitch, and so on.
Said memory means comprise, for example, flip-flop circuits which employ two transistors respectively and control switching-on and switching-off of tone signals from corresponding tone generators.
However, the conventional signal-selecting system has the disadvantage that as many memory means are required as there are keyswitches, and when a flip-flop circuit is used for the memory means, many transistors are required, especially for an instrument having keyswitches for several octaves.
Further, because the many keyswitches for several octaves are connected in series, it becomes necessary that these keyswitches have a very high reliability so as to present defective operation such as frequent break-down due to poor contacts of the keyswitches.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a novel and improved signal-selecting system for a keyboard type electronic musical instrument.
Another object of the present invention is to provide a compact and reliable signal-selecting system comprising a plurality of keyswitches corresponding to several octaves and twelve memory means corresponding to one octave.
A further object of the present invention is to provide an improved signal-selecting system comprising tone generators corresponding to one octave and more than one frequency divider, and which is capable of providing the selected tone signal having the lowest frequency from among the tone signals corresponding to several octaves when a plurality of keyswitches are depressed simultaneously.
A still further object of the present invention is to provide an improved signal-selecting system comprising tone generators corresponding to one octave and more than one frequency multiplier, and which is capable of providing the selected tone signal having the highest frequency from among the tone signals corresponding to several octaves when a plurality of keyswitches are depressed simultaneously.
A further object of the present invention is to provide an improved signal-selecting system comprising a plurality of keyswitches corresponding to several octaves and an octave-selecting means for detecting the keyswitch group corresponding to the highest or lowest octave.
These objects are achieved by employing a signal-selecting system according to the present invention which comprises a plurality of keyswitches which are actuated by corresponding keys of a keyboard, said keyswitches being in a range of more than two octaves and being divided into a number of keyswitch groups equal to the number of octaves;;
a memory circuit having a plurality of memory means corresponding to the notes of one octave;
a plurality of tone signal sources for generating the tone signals corresponding to the notes of one octave;
a plurality of signal-switching means corresponding to the notes of one octave, each of said signal-switching means being connected between the corresponding memory means and the corresponding tone signal source respectively, said switching means switching a selected tone signal according to the operation of said memory means;
one or a plurality of frequency dividers connected in series, said frequency dividers dividing the frequency of the tone signal applied thereto by a factor of two;
key-selecting means for selecting the extreme keyswitch of the keyswitches which are closed simultaneously in each of said keyswitch group and supplying electric power to the corresponding memory means so as to set it, keyswitches which are in different keyswitch groups and in one or more than one octave relation to each other being connected in common;
an octave-selecting means for detecting the extreme group of the keyswitch groups containing the keyswitches which are closed simultaneously and then switching off the supply of electric power to the keyswitch groups keyswitches of which are set in the opposite direction from the key switches in said detected extreme keyswitch group, said octave-selecting means selecting the number of said frequency dividers to be operated by applying the switched tone signal directly to the first one of said frequency dividers so that the frequency of said switched tone signal is divided in turn by all of said frequency dividers connected in series or by bypassing some of said frequency dividers so that the frequency of said switched tone signal is divided in turn by the rest of the frequency dividers, the divided frequency of the tone signal provided at an output terminal of the signal-selecting system corresponding to the extreme keyswitch of the keyswitches which are closed simultaneously in the whole range;
a detecting means for detecting the moment when another extreme keyswitch of said plurality of keyswitches is closed and then for generating a reset pulse for resetting the memory means which has been set previously; and
a power source which is connected through said octave selecting means and said detecting means, respectively to each of said keyswitch groups.
BRIEF DESCRIPTION OF THE DRAWINGS
These objects and other features of the present invention will be made clear from the following detailed description of the invention considered together with the accompanying drawings wherein:
FIG. 1 is a schematic circuit diagram for explaining a signal selecting operation of a signal-selecting system for a keyboard type-electronic musical instrument according to the present invention.
FIG. 2 is a circuit diagram, of an example of memory means and detecting means shown in FIG. 1.
FIG. 3 is a schematic circuit diagram of a signal-selecting system for a keyboard type electronic musical instrument according to the present invention.
FIG. 4 is a circuit diagram of an embodiment of the signal-selecting system of the present invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
The signal-selecting system of the invention will be described, for convenience, as using transfer type keyswitches connected in series as the key-selecting means. However, the present invention can make use of substantially any kind of key-selecting means which is capable of producing voltage at an output terminal corresponding to the extreme key depressed simultaneously. For example, the present invention can use as a key-selecting means the selecting circuit which is disclosed in U.S. Pat. No. 3,585,892 of the same applicant which comprises a totem-pole connection of transistors, each base being connected to a corresponding keyswitch. Therefore, the present invention is not restricted to a key-selecting means which uses transfer type keyswitches connected in series.
Referring to FIG. 1, there will be described the general operation of a signal-selecting system for a keyboard type electronic musical instrument. A plurality of keyswitches K 1 , K 2 , K 3 . . . , K n are connected to corresponding keys of the electronic musical instrument, respectively. The break-contacts of the keyswitches are connected in series to the movable-contacts of the subsequent keyswitches, each respectively, as shown in FIG. 1. That is, the break-contact of the keyswitch K 1 is connected to the movable-contact of the next keyswitch K 2 , and so on. The make-contacts of the keyswitches are connected to a corresponding memory means in a memory circuit 1, and the movable-contact of the keyswitch K 1 is connected to a power source through a detecting means 22 and a terminal 21. Therefore, even when a plurality of the keyswitches, for example the keyswitches K 1 and K 2 , are closed simultaneously, the electric power is only applied to the memory means corresponding to the keyswitch K 1 because the movable-contact of the keyswitch K 2 is connected to the break-contact of the keyswitch K 1 and so the keyswitch K 2 is not connected to the terminal 21.
The memory circuit 1 contains as many memory means as there are keyswitches K 1 , K 2 , K 3 , . . . , K n , and each of the memory means is connected to the corresponding keyswitch, respectively. A flip-flop circuit employing two transistors may be used for the memory means.
Further, a plurality of tone signal sources 2 equal in number to the number of the keyswitches K 1 , K 2 , K 3 , . . . , K n are connected to the corresponding memory means, respectively. The switching-on and off of the tone signal from the tone signal source is controlled by the memory means, e.g., according to change of the operating condition of the flip-flop circuit. Then, the tone signal is provided to an output terminal 20 through the memory circuit 1.
A D.C. voltage is applied at the terminal 21 as a power source for the system. Further, the operating condition of the flip-flop circuit of the memory circuit 1 is changed through the detecting means 22 by the electric power applied to the terminal 21. The detecting means detects each time when any of the movable-contacts of the keyswitches is closed against a make-contact or when more than two of the memory means are set simultaneously, and resets all the flip-flop circuits of the memory circuit 1. Then, a flip-flop circuit is set corresponding to the keyswitch for the lowest or highest frequency. Such a signal selecting operation is described in more detail in the following.
Referring to FIG. 2 which is an example of a circuit configuration corresponding to the schematic diagram of FIG. 1, the same parts as those in FIG. 1 are designated by the same reference numerals and the memory circuit 1 is formed of a plurality of flip-flop circuits, each comprising two transistors T 1 and T 2 and resistors R 1 and R 2 , T 3 and T 4 and identical resistors R 1 and R 2 , and so on. Resistors R 3 and R 4 are connected in series with resistors R 1 and ground. Signal-switching means are provided comprised of diodes D 1 , D 2 , . . . , and each of them is connected between the corresponding tone generator S 1 , S 2 . . . , and output terminal 20 through a junction between resistors R 3 and R 4 . Resistor R 5 is connected between the junction between resistors R 1 , R 2 and the collector of transistor T 1 , T 2 . . . , and the junction between the tone generator and the diode. For simplicity, the signal-switching means is shown in combination with the memory circuit in FIGS. 1 to 4. The detecting means 22 in FIGS. 2 and 4 is composed of three switching amplifiers, a differentiator and a rectifier. These are connected as follows. One switching amplifier is composed of a transistor T 11 , the emitter of which is connected to the electric power source through a terminal 21 for the detecting means power supply, the collector of which is connected through a collector resistor R 11 to ground, and the base of which is supplied with ground potential when all of the keyswitches are closed. The differentiator is composed of a capacitor C 1 , one end of which is connected to the collector of the transistor T 11 and resistor R 12 , which is connected between ground and the other end of the capacitor C 1 . The rectifier is composed of a diode D 11 , which is connected in parallel with the resistor R 12 and the anode of which is connected to ground. The second switching amplifier is composed of a transistor T 12 , the emitter of which is connected to ground, the collector of which is connected through a collector resistor R 13 and the terminal 21 to the electric power source, and the base of which is connected to the cathode of the diode D 11 . The third switching amplifier is composed of a transistor T 13 , the emitter of which is connected to ground, the collector of which is connected through a collector resistor R 14 and the terminal 21 to the electric power source, and the base of which is connected to the collector of the transistor T 12 .
The transistors T 11 and T 12 are normally switched off and the transistor T 13 is normally switched on when none of the keyswitches are closed. The differentiator differentiates the voltage change at the collector of the transistor T 11 . The rectifier rectifies the output of the differentiator and produces a positive going trigger pulse. The switching amplifiers with transistors T 12 and T 13 amplify and shape the input trigger pulse so as to produce a positive going rectangular pulse which resets the flip-flop circuits in the memory means 1. When the keyswitch K 1 is closed by depressing the corresponding key, a current flows to the transistor T 1 through a resistor R 8 and the transistor T 1 is saturated.
On the other hand, a transistor T 11 in the detecting means 22 is also saturated because the current flowing to the transistor T 1 at closing of the keyswitch K 1 becomes the base current of the transistor T 11 . By differentiating this instant current with a capacitor C 1 , a positive pulse is provided at the base of a transistor T 12 , and thereby the transistor T 12 is saturated and a transistor T 13 is cut off.
The collector of the transistor T 13 is connected through resistors R 7 to the base of each transistor T 2 , T 4 , . . . , of the flip-flop circuits, respectively. Therefore, when the transistor T 13 is cut off, base current flows to the transistors T 2 , T 4 , . . . through a resistor R 14 . Then, the transistors T 2 , T 4 , . . . , are saturated, and this state is maintained.
However, in the flip-flop circuit comprising the transistors T 1 and T 2 , because the transistor T 1 is saturated, as described above, by the closed keyswitch K 1 , the transistor T 2 is cut off when the positive pulse disappears, and this state is held even after the keyswitch K 1 is opened.
Resistance values of resistors R 1 , R 2 , R 3 and R 4 of the flip-flop circuit have values in the relation of the following equation:
R 2 /R 1 + R 2 > R 4 / R 3 + R 4 > 0.
When the transistor T 1 is saturated, the diode D 1 is conductive, and accordingly a tone signal S 1 corresponding to the keyswitch K 1 is provided to the output terminal 20. On the other hand, the diode D 2 in the second memory means is cut off because the transistor T 3 is cut off and because of the above relation, R 2 / R 1 + R 2 > R 4 / R 3 + R 4 , so that other tone signals S 2 , S 3 . . . are not supplied to the output terminal 20. Consequently, there is provided a signal switching operation for the selected tone signal.
Then, when another keyswitch K 2 is closed, with a voltage applied to the terminal 21, a current flows to the transistor T 3 through the transistor T 11 of the detecting means 22, the keyswitches K 1 and K 2 and the resistor R 8 , and the transistor T 3 is saturated. As in the case of keyswitch K 1 instant of closing the keyswitch K 2 is detected by the transistor T 11 , and the transistor T 13 is cut off through the transistor T 12 , so that the transistors T 2 , T 4 , . . . are saturated through the resistors R 7 , respectively and this state is held. At saturation of the transistor T 2 , the transistor T 1 , and so also the diode D 1 are cut off, and accordingly the tone signal S 1 is not supplied to the output terminal 20. On the other hand, the transistor T 3 is saturated due to the closing of the keyswitch K 2 , so that the diode D 2 is conductive and the other diodes are cut off in the same manner as described above. Accordingly, only the tone signal S 2 corresponding to the keyswitch K 2 is selectively supplied to the output terminal 20.
There has been described hereinbefore the fundamental signal selecting operation for a keyboard type electronic musical instrument, and the operation of the signal selecting system of the invention is also similar to the above. However, according to the present invention, the signal selecting operation for a plurality of keyswitches corresponding to several octaves can be provided by employing only the memory means and the tone generators corresponding to one octave. Such a novel and improved signal selecting system will now be described.
Referring to FIG. 3 which shows a schematic diagram of the signal selecting system of the present invention, the same parts as those shown in FIG. 1 are designated by the same reference numerals, and the system is shown for an instrument having keys corresponding to three octaves.
A plurality of keyswitches K 1 , K 2 , . . . , K 26 , K 27 are divided into three keyswitch groups, groups 31 for K 1 to K 12 , group 32 for K 13 to K 24 and group 33 for K 25 to K 36 , corresponding to the respective octaves. In each of the keyswitch groups, each of the break-contacts of the keyswitches is connected to the movable-contact of the subsequent keyswitch, respectively, so as to carry out the signal selecting operation when a plurality of keyswitches are depressed simultaneously, as described hereinbefore referring to FIG. 1. On the other hand, the make-contacts of the keyswitches which are in an octave relation, i.e., the keyswitches K 1 , K 13 and K 25 , and K 2 , K 14 and K 26 and so on, are connected in common, respectively.
The memory circuit 1 is one similar to that of FIG. 1, and it has as many memory means as the number of tones corresponding to one octave, i.e., 12 memory means, each of which consists of a conventional flip-flop circuit, for example. Tone signal sources 2 are also similar to those of FIG. 1 and they provide the tone signals for one octave. Each of the tone signal sources 2 is connected to the corresponding one of the 12 flip-flop circuits, respectively, and the switching on and off of the tone signal is controlled according to the condition of the flip-flop circuits.
The frequency of the tone signal provided to the terminal 20 through the memory circuit 1 is divided by frequency dividers 3 and 4 by a factor of two, respectively. By means of an octave-selecting means 5, the tone signal is applied to the frequency divider 4 through the other frequency divider 3 or directly through a gate circuit 13 instead of through the divider 3.
The octave-selecting means 5 contains three detectors 6, 7 and 8 which are coupled to the respective keyswitch groups in such a way that the detector 6 is operated when a keyswitch in the first keyswitch group 31 of K 1 to K 12 is closed, the detector 7 is operated when a keyswitch of the second group 32 is closed, and the detector 8 is operated when a keyswitch of the third keyswitch group 33 of K 25 , K 26 , . . . , K 36 is closed.
The octave-selecting means 5 further contains two memory circuits 11 and 12 which have set terminals connected to the detectors 7 and 8, respectively, and memory circuit 11 has a reset terminal connected to detector 6 and memory circuit 12 has a reset terminal connected to detectors 7 and 8, so that the memory circuit 11 is set by a pulse provided from the detector 7 and reset by a pulse provided from the detector 6, and the memory circuit 12 is set by a pulse from the detector 8 and reset by pulses from the detectors 6 and 7. When the memory circuit 11 is set, the gate circuit 13, which is connected thereto, is conductive and the tone signal provided to the terminal 20 is directly applied to the frequency divider 4 jumping the other frequency divider 3. Then, the tone signal divided by the frequency divider 4 is provided to an output terminal 23. In this case, the frequency of the tone signal provided at the output terminal 23 is a half that of the tone signal provided at the terminal 20.
There is further provided another gate circuit 14 which bypasses gate circuit 13 and frequency divider 4, and which is connected to the memory circuit 12 and is conductive when memory circuit 12 is set and which provides the tone signal at the terminal 20 directly to the output terminal 3 without passing through the frequency dividers 3 and 4. Therefore, the frequency of the tone signal provided at the output terminal 23 is the same as that of the tone signal provided at the terminal 20. When neither of the gate circuits 13 and 14 are conductive, the tone signal provided at the terminal 20 is applied to the frequency divider 3, and the output signal therefrom is further applied to the other frequency divider 4. Therefore, in this case, the tone signal provided to the output terminal 23 has a frequency which is a quarter of that of the tone signal provided to the terminal 20.
The octave-selecting means 5 further contains two switching circuits 9 and 10 connected between keyswitch group 32 and detector 7 and between keyswitch group 33 and detector 8, respectively, and which are normally condutive. The switching circuit 9 is connected to the detector 6 through a diode D 12 and it is cut off on the operation of the detector 6. The switching circuit 10 is connected to the detectors 6 and 7 through diodes D 13 and D 14 , respectively, and it is cut off on the operation of the detector 6 or 7.
The detecting means 22 is similar to that of FIG. 1. Upon detecting the instant when the keyswitches are closed, the detecting means 22 resets all of the flip-flop circuits of the memory circuit 1, and thereby always only one tone signal is selectively provided to the terminal 20. The operation of the detecting means 22 is described in detail hereinbefore in connection with FIG. 2. In the following, there will be described in more detail the operation of the signal selecting system shown in FIG. 3.
Referring to FIG. 4 which shows a circuit configuration of an embodiment of the signal selecting system of the invention, the same parts as those of FIG. 3 are designated by the same reference numerals. The memory circuit 1 and the tone generators 2 are shown in a block, respectively because an example of practical circuit configurations thereof are shown in FIG. 2. However, the number of the memory means and the tone generators present of course correspond to the notes of one octave, i.e., only 12, respectively,
In FIG. 4, a flip-flop circuit is employed for each of the frequency dividers 3 and 4. The frequency divider 3 divides the frequency of the tone signal by a factor of two, and the frequency divider 4 divides the frequency of the tone signal provided from the frequency divider 3 by a factor of two.
The detectors 6, 7 and 8 comprise transistors T 15 , T 16 and T 17 and grounded resistors R 15 , R 16 and R 17 connected to the collectors, respectively. Resistors r 16 and r 17 are connected across the base and emitter of transistors 16 and 17, respectively. When the keyswitches of the keyswitch groups 31 (K 1 , K 2 , . . . , K 12 ), , 32 (K 13 , K 14 , . . . , K 24 ) AND 33 (K 25 , K 26 , . . . , K 36 ) are closed, respectively, the transistors T 15 , T 16 and T 17 are saturated, respectively, and it is thus detected that the keyswitches of each of the keyswitch groups are closed.
The memory circuits 11 and 12 also comprise flip-flop circuits consisting of transistor T 21 and T 22 , and T 23 and T 24 , respectively. The memory circuit 11 is set through a diode D 16 when a positive voltage is provided at the collector of the transistor T 16 of the detector 7, and it is reset through a diode D 15 when a positive voltage is provided at the collector of the transistor T 15 of the detector 6. The memory circuit 12 is set through a diode D 19 when a positive voltage is provided at the collector of the transistor T 17 of the detector 8, and it is reset through diode D 17 or D 18 when a positive voltage is provided at the collector of the transistor T 15 or T 16 of the detector 6 or 7, respectively.
The anode of a diode D 22 forming part of the gate circuit 13 is connected to the collector of the transistor T 21 of the memory circuit 11 through a resistor R 26 , and the cathode of the diode D 22 is connected to the terminal 20. Therefore, when the transistor T 21 of the memory circuit 11 is cut off, the diode D 22 is conductive and by-passes the frequency divider 3, so that the tone signal provided at the terminal 20 is applied to the second frequency divider 4. When the transistor T 21 of the memory circuit 11 is saturated, the diode D 22 is not conductive.
Similarly, a diode D 21 forming part of the gate circuit 14 is connected to the collector of transistor T 23 of memory circuit 12 and is conductive when the transistor T 23 of the memory circuit 12 is cut off and gate circuit 14 thus by-passes the frequency dividers 3 and 4, so that the tone signal provided at the terminal 20 to which the cathode of diode D 21 is connected is directly applied to the output terminal 23. When the transistor T 23 of the memory circuit 12 is saturated, the diode D 22 is cut off.
The frequency dividers 3 and 4 are arranged to be triggered by a negative pulse. A capacitor C 4 differentiates the fall of the tone signal and provides a negative pulse to trigger the frequency divider. A negative pulse having the tone signal frequency is provided at the output terminal 23.
Accordingly, even when the frequency of the tone signal provided at the terminal 20 is not varied, the tone signal provided at the output terminal 23 has in relation to the frequency of the tone signal at terminal 20, a frequency lower by two octaves when neither of the gate circuits 13 and 14 are conductive, a frequency lower by one octave when only the gate circuit 13 is conductive and the same frequency when the gate circuit 14 is conductive.
The switching circuits 9 and 10 comprise transistors T 18 and T 19 and resistors R 18 and R 19 connected to the bases thereof, respectively. Normally, both of the switching circuits 9 and 10 are conductive due to the base current flowing through the resistors R 18 and R 19 , respectively. At this time, the base currents of the transistors T 18 and T 19 become the base currents of the transistors T 16 and T 17 of the detectors 7 and 8, respectively. However, the resistance values of the resistors R 18 and R 19 are made sufficiently large and the base current is shunted by resistors r 16 and r 17 , respectively, so that the transistors T 16 and T 17 of the detectors 7 and 8 are not saturated.
When the transistor T 15 of the detector 6 is saturated, the base current of the transistor T 18 in the switching circuit 9 flows through the resistor R 18 from the collector of the transistor T 15 through the diode D 12 , and so the transistor T 18 is cut off. Accordingly, electric power is not provided to the second keyswitch group K 13 , K 14 . . . , K 24 . Similarly, the switching circuit 10 is cut off when the detector 6 or 7 is operated, and so electric power is not provided to the third keyswitch group K 25 , K 26 , . . . , K 36 .
The detecting means 22 is similar to that of FIG. 2. Upon detecting the instant key when the keyswitches are closed, the detecting means 22 resets all of the flip-flop circuits of the memory circuit 1, and thereby only one tone signal is selectively provided to the terminal 20.
As described hereinbefore, it will be understood that the octave-selecting means, which comprises the detectors 6, 7 and 8, the switching circuits 9 and 10, the memory circuits 11 and 12, and the gate circuits 13 and 14, detects the keyswitch groups containing the keyswitches which are closed and selects the extreme keyswitch group corresponding to the lowest or highest tone in these keyswitch groups, and then it stops providing electric power to all the keyswitch groups for tones above or below, as the case may be, the selected extreme keyswitch group. Further, at the same time, the octave-selecting means sets the frequency dividers so as to provide the tone signal having the frequency corresponding to the extreme key for the lowest or highest tone signal among the keys on the same keyboard which are depressed simultaneously.
Because the keyswitches are connected in series, as described hereinbefore, in each of the keyswitch groups, it is clear that a signal selecting operation is provided for each of the keyswitch groups. For example, in the first keyswitch group of K 1 , K 2 , . . . , K 12 , the signal selecting operation is described in connection with FIG. 1. Hereinafter there will be described in detail the signal selecting operation between the keyswitch groups.
When the keyswitch K 25 is closed, for example, a voltage applied to the terminal 21 is supplied to one flip-flop circuit of the memory circuit 1 corresponding to the keyswitches K 1 , K 13 and K 25 through the detecting means 22, the detector 8, the switching circuit 10 and the keyswitch K 25 , and said one flip-flop circuit is set. Therefore, a tone signal corresponding to the tone for keyswitch K 25 , but which can be divided to produce tones corresponding to keyswitches K 13 and K 1 , is terminal 20.
On the other hand, by the operation of the detector 8, the memory circuit 12 is set, and then the gate circuit 14 is made conductive. Therefore, the tone signal at the terminal 20 is supplied to the output terminal 23 as it is.
When the keyswitches K 13 and K 25 are closed simultaneously, one flip-flop circuit corresponding to the keyswitches K 1 , K 13 and K 25 is again set through the detector 7, the switching circuit 9 and the keyswitch K 13 . On the other hand, the switching circuit 10 is cut off by the operation of the detector 7, so that the detector 8 is not operated. Further, by the operation of the detector 7, the memory circuit 12 is reset and the memory circuit 11 is set. Consequently, the gate circuit 14 is closed and the gate circuit 13 is made conductive. Accordingly, the frequency of the tone signal at the terminal 20 is divided by the frequency divider 4 and the tone signal having a frequency of a half of that of the signal at the terminal 20 is provided to the output terminal 23.
When the keyswitches K 1 , K 13 and K 25 are closed simultaneously, one flip-flop circuit corresponding to these keyswitches is set through the detector 6 and the keyswitch K 1 , and the corresponding tone signal is switched on. On the other hand, by the operation of the detector 6, the switching circuits 9 and 10 are cut off, and so there is no current flowing to the detectors 7 and 8. Consequently, the memory circuits 11 and 12 are reset, and so the gate circuits 13 and 14 are cut off. Accordingly, the frequency of the tone signal at the terminal 20 is divided by the frequency dividers 3 and 4 by a factor of two, respectively so that there is provided a tone signal having a frequncy one quarter of that of the signal at the terminal 20 at the output terminal 23.
As described above, even when a plurality of keyswitches are closed simulaneously, always only the lowest tone signal is provided preferentially. It is of course possible to provide preferentially the highest tone by modifying slightly the manner of triggering of the switching circuits 9 and 10 and the gate circuits 13 and 14 of the system described above.
As described hereinbefore, according to the present invention, by employing the memory means and tone generators corresponding to the notes of one octave, a signal selecting operation can be performed for the keyswitches corresponding to the notes of several octaves. Therefore, there are the great advantages that the number of electronic components for the signal selecting system can be reduced, that because the number of the keyswitches which are to be connected in series can be reduced when transfer type keyswitches are used, the troubles due to poor contact of the keyswitches can be greatly reduced and a high reliability is obtained even when using the usual inexpensive transfer type keyswitches which are not so high in quality, and further that manufacturing steps can be reduced because of a reduced number of wiring connections in the keyswitches, and so on.
While a particular embodiment of the invention has been described hereinbefore, it will be apparent that various modifications can be made in the form and construction thereof. For example, other circuit besides the flip-flop circuit may be used for the memory means of the memory circuit, the frequency dividers and the memory circuit of the octave-selecting means. The same is true with respect to the signal-switching device, the switching circuit, and the detector. Moreover, there has been described above the modification in which the system selects the highest frequency tone signal wheras the parts can be easily modified to select the lowest frequency tone signal.