JPS6210792Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an electronic keyboard instrument, and in particular, an object of the invention is to provide an electronic keyboard instrument that can generate intermediate tones when a plurality of keys are operated simultaneously.

FIG. 1 shows an example of a signal generation circuit for a conventional electronic keyboard instrument. In the figure, 1 is a voltage controlled oscillator, 2 is a resistor ladder circuit that applies a control voltage to the control terminal of this voltage controlled oscillator, and 3 is a group of key switches.
In other words, one end of the key switch group 3 is connected to a voltage source 4 having a constant voltage, and the other end is connected to the resistor ladder circuit 2.
is connected to the connection point of the series resistor _R1 .

According to such a configuration, when any one switch in the key switch group 3 is turned on, the voltage of the voltage source 4 is applied to the ladder circuit 2 through that switch.
is supplied to the connection point. By setting the resistance values of the series resistor R ₁ and the parallel resistor R ₂ of the resistor ladder circuit 2 to be equal to each other, when each switch of the switch group 3 is turned on sequentially from the end, a voltage is applied to the voltage controlled oscillator 1. The voltage changes along an exponential curve. Therefore, the oscillation frequency of the oscillator 1 changes according to the frequency of the 12 equal temperament scale, and a signal of any pitch can be obtained by operating the keyboard. By the way, in a conventional circuit, for example, if two key switches are operated at the same time, oscillator 1
Since the voltage generated by the switch closer to the switch is higher, the oscillator 1 determines the oscillation frequency according to the higher voltage. In other words, in conventional electronic keyboard instruments of this type, even if multiple keys are operated at the same time, the higher note is output with priority.

By the way, for example, when playing a song like the blues, 1/4 tone is required. Ordinary musical instruments, such as keyboard instruments such as pianos and organs, have a 1/2 tone.
In other words, the scale is determined by the pitch of each chromatic scale. On a piano or organ, if you operate multiple keys at the same time, all the sounds corresponding to those keys will be produced. For this reason, in order to produce a 1/4-tone sound, a playing method is used in which adjacent keys are operated simultaneously, making it sound as if a 1/4-tone sound is being produced.

The purpose of this invention is to provide an electronic keyboard instrument that can produce an intermediate sound when two keys are operated simultaneously.

This device monitors the current flowing through the resistor ladder circuit, detects an increase in the current, detects the simultaneous operation of multiple keys, and uses the detection signal to reduce the oscillation frequency of the voltage-controlled oscillator by 1/2. This controls the sound so that only four tones are lowered.

An embodiment of this invention will be described below in detail with reference to the drawings.

FIG. 2 shows an embodiment of this invention. In FIG. 2, parts corresponding to those in FIG. 1 are denoted by the same reference numerals and redundant explanation thereof will be omitted. In the figure, 1 is a voltage controlled oscillator, 2 is a resistance ladder circuit, and 3 is a group of key switches. In this invention, a circuit 5 for detecting an increase in the current flowing through the resistance ladder circuit 2 is provided. This detection circuit 5 can be constituted by, for example, a differential operational amplifier 6. The non-inverting input terminal of the differential operational amplifier 6 is connected to a common potential point, and the inverting input terminal is connected to the ground line 7 of the resistance ladder circuit 2. The ground line 7 of the resistor ladder circuit 2 is connected to the negative voltage source 8 through a resistor R ₃ , and the output of the operational amplifier 6 is connected to the ground line 7 of the resistor ladder circuit 2 through a resistor R ₄ .

In the above configuration, when only one key switch is turned on, the resistance of the resistor _R3 is adjusted so that the ground line 7 of the resistor ladder circuit 2 becomes exactly at the common potential due to the voltage drop caused by the current flowing through the resistor _R3 . Set the value. Therefore, when two key switches are operated at the same time, the current flowing through the resistor _R3 increases and the voltage drop increases, so that the potential of the ground line 7 of the resistor ladder circuit 2 is biased to the positive side with respect to the common potential. However, this potential change is caused by the operational amplifier 6
The amplifier 6 outputs a negative polarity voltage, and supplies this output voltage to the ground line 7 of the resistance ladder circuit 2 through the resistor _R4 . Therefore, the potential of the ground line 7 of the resistance ladder circuit 2 is returned to the potential of the other input terminal of the amplifier 6, that is, the common potential. Therefore, the ground line 7 of the resistance ladder circuit 2 is controlled so as to be always held at the common potential. After all, when two key switches are operated simultaneously, the amplifier 6 outputs a negative voltage. Therefore, the polarity of the output voltage of the amplifier 6 is inverted through the inverter 9, for example.
A switch element 10 such as an FET is turned on, and by turning on the switch element 10, the voltage division ratio of the voltage divider circuit 11 connected between the resistor ladder circuit 2 and the oscillator 1 is changed, and the control voltage is supplied to the oscillator 1. is configured to reduce by a voltage equivalent to 1/4 tone.

As is clear from the above explanation, according to this invention, by operating two key switches simultaneously, an increase in the current flowing through the resistance ladder circuit 2 is detected, and this detection output is used to generate the voltage controlled oscillator 1.
Since the control voltage supplied to the
The oscillator 1 can output a sound frequency that is 1/4 tone lower, making it easier to play songs such as blues, and improving the performance effect.

In the above description, an embodiment has been described in which the control voltage supplied to the oscillator 1 by the switch 10 is lowered by a voltage corresponding to 1/4 tone, but various other methods are also conceivable. For example, the oscillation time constant of the oscillator 1 can be changed by turning on and off the switch element 10, and the oscillation frequency can be lowered by 1/4 tone. Furthermore, the output voltage of the amplifier 6 is applied to a variable impedance element, and the change in the impedance of this variable impedance element reduces the charge/discharge current applied to the oscillation time constant circuit of the oscillator 1, thereby reducing the oscillation frequency by 1/2.
It can also be configured to lower frequencies corresponding to four tones.

Also, in the above description, when two keys are operated at the same time, the oscillation frequency of oscillator 1 is lowered by the amount equivalent to 1/4 tone, but it is not necessarily limited to 1/4 tone. It is easy to understand that it can be configured to output a sound in between when operated at the same time, and that the settings can be set arbitrarily.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram showing an example of a conventional electronic keyboard instrument, and FIG. 2 is a connection diagram showing an embodiment of this invention. 1... Voltage controlled oscillator, 2... Resistance ladder circuit, 3... Key switch group, 4... Voltage source, 5
. . . A detection circuit that detects that a plurality of key switches are turned on; 10 .
...Similar voltage divider circuit.

Claims (1)

[Scope of utility model registration request] A resistance ladder circuit, a key switch that selectively applies a constant voltage to the connection point of each resistor of this resistance ladder circuit, and a voltage-controlled oscillation circuit whose oscillation frequency is controlled by the voltage generated at one end of the resistance ladder circuit. and a circuit that detects the current flowing through the resistor ladder circuit to detect that multiple key switches are turned on, and the detection output of this detection circuit adjusts the oscillation frequency of the voltage controlled oscillator to correspond to the pitch between the key switches. An electronic keyboard instrument comprising means for controlling the frequency to a certain frequency.