JPS6230071Y2 - - Google Patents

Description

[Detailed description of the invention] This invention relates to a sound source waveform conversion circuit for converting the sound source signal waveform of an electronic musical instrument into a complex waveform containing many harmonic components to generate musical tones with rich and varied tones. It is something.

Waveforms containing relatively many harmonic components such as square waves, sawtooth waves, and triangular waves are used as sound source signal waveforms for electronic musical instruments, but these waveforms alone are insufficient to generate rich musical tones with a wide variety of variations. I can't.

Therefore, it is known that, for example, a sawtooth wave sound source signal is pulse width modulated and converted into a variable duty rectangular wave signal for use.

Figure 1 is a block diagram showing an example of such an electronic musical instrument, in which a pitch voltage is generated from the keyboard circuit 1 when a key is pressed.
Generates KV and key press signal KON. A sawtooth wave sound source signal with a frequency corresponding to the sound pitch voltage KV is generated from a voltage controlled oscillator VCO as a sound source signal generator. The sawtooth wave signal a is compared with the low frequency signal b generated from the modulation signal generator 5 in the comparator 4 of the pulse width modulation circuit 3 as shown in FIG. The signal is converted into a duty-variable rectangular wave signal c as shown in FIG. This sound source signal c converted into a rectangular wave is passed through a voltage-controlled filter VCF6 and a voltage-controlled amplifier VCA7, and is generated by an envelope waveform generated by envelope waveform generators EG8 and EG9 in synchronization with the key press signal KON. Tone and envelope are formed. The sound is produced by a sound system 10 including an amplifier, a speaker, and the like.

However, simply converting into a variable duty rectangular wave in this way limits the timbre of musical tones, and it is still not possible to obtain musical tones with a satisfactory variety.

This idea was made in view of the above points,
A musical sound with a rich and varied tone by converting the waveform of a sound source signal such as a sawtooth wave, triangular wave, or sine wave whose level changes at a period corresponding to the pitch frequency into a complex waveform containing many harmonic components. The purpose is to obtain.

In order to achieve the above object, this invention provides control for generating a first control signal and a second control signal, each of which is a constant level or a signal whose level changes over time over a period longer than the period of the sound source signal. a signal source, a comparator that compares the level of the sound source signal and the level of the first control signal, and a gate circuit that intermittently outputs the second control signal based on the comparison output of the comparator; A sound source waveform of an electronic musical instrument, comprising: an arithmetic circuit that calculates the output signal and the sound source signal in a section where the output signal of the gate circuit exists to change the level or rate of change of the sound source signal. It provides a conversion circuit.

According to this sound source waveform conversion circuit, the level of the sound source signal or its rate of change is determined according to the level of the second control signal in an interval determined according to the level of the first control signal within the period of the sound source signal. The waveform suddenly changes and is converted into a complex waveform containing many harmonic components.

Hereinafter, embodiments of this invention will be described with reference to FIG. 3 and subsequent figures of the accompanying drawings.

FIG. 3 is a block circuit diagram of one embodiment of this invention. In the figure, 11 and 12 are control signal sources for changing the sound source waveform, and VR ₁ and VR ₂ are power supply +V
and a variable resistor as a potentiometer that outputs a DC voltage that is varied by a knob on the panel surface, 13 and 14 are sawtooth waves,
Triangle wave and sine wave low frequency signals (input signal
It is a low frequency oscillator that generates a signal with a very low frequency relative to Vi. S ₁ and S ₂ are the DC voltages (constant level signals) from variable resistors VR ₁ and VR _2, respectively, and the low frequency signals of each waveform of the low frequency oscillators 13 and 14 (with a time relationship longer than the period of the sound source signal). A signal whose level changes over time) is arbitrarily selected, and the first control signal V _c1 and the second control signal V _{c2 are}
This is a selector switch that outputs as follows. These selector switches S ₁ and S ₂ are controlled by knobs on the panel.
They can be switched independently or in conjunction with each other. Furthermore, the same control signal sources 11 and 12 may be used.

15 is a comparator circuit that connects the input signal Vi and the control signal V _c1
The output is set to high level "1" only when Vi>V _c1 . 16 is a gate circuit whose opening/closing is controlled by the output of the comparator 15;
The control signal V _c2 is passed only when the output of the control signal V c2 is "1". 17 is an arithmetic circuit which adds or multiplies the input signal Vi and the gate output Vg and outputs the result. 18 is an input terminal, and 19 is an output terminal.

Therefore, let us consider the case where the changeover switches S ₁ and S ₂ of each control signal source are set to output the DC voltage from the variable resistors VR ₁ and VR ₂ as the control signals V _c1 and V _c2 as shown in the figure. , the operation of this embodiment will be explained with reference to FIG.

When a sawtooth wave sound source signal as shown in FIG. 4A is input as the input signal Vi to the input terminal 18,
The comparator circuit 15 compares it with the control signal V _c1 output from the control signal source 11 . And Vi>V
Only when _c1 , the output of the comparator circuit 15 becomes "1" and the gate circuit 16 is opened. Therefore, the constant level DC control signal V _c2 shown by the dashed line in FIG. 17.

The arithmetic circuit 17 calculates the gate output Vg and the input signal (sound source signal) Vi in the section where the output signal of the gate circuit 16 exists, and changes the level of the input signal Vi or its rate of change, as shown in FIG. An output signal Vo having a waveform as shown in (in the case of addition) or 2 (in the case of multiplication) is output to the output terminal 19.

Therefore, the signal level of the sawtooth wave as the input signal Vi suddenly changes in the middle of each cycle and is converted into a complex waveform, and the magnitude of the change A and the width of the changing part B (see Figure 4 C) ) are the control signals V _c2 , V _c1
can be arbitrarily varied depending on the level.

Therefore, a low frequency signal such as a sawtooth wave, a triangular wave, or a sine wave generated by the low frequency oscillators 13 and 14 is selected from the control signal sources 11 and 12 to generate the control signal V _c1 ,
When it is output as V _c2 , the magnitude A of the change in the waveform of the output signal Vo and the width B of the changing portion shown in Figure 4 C vary periodically, resulting in a waveform with even more variation. . Then, the control signal V _c1 ,
The manner of its fluctuation varies depending on the waveform of V _c2 .

Furthermore, the envelope waveform generator 8 or 9 in FIG. 1 can also be used as one or both of the control signal sources 11 and 12.
In that case, an envelope waveform as shown in Fig. 5 generated as the control signal V _c1 or V _c2 in synchronization with the key press signal KON, that is, the initial level.
IL, attack level AL, sustain level
A waveform with SL will be used. Therefore, when a key is pressed, the waveform of the musical tone output signal changes according to the level of this envelope waveform, and the tone changes.

Next, FIG. 6 is a block circuit diagram showing another embodiment of this invention, in which the same parts as in FIG. 3 are given the same reference numerals, and the explanation of those parts will be omitted.

In the figure, 20 is an inverting amplifier that inverts the control signal V _c1 output from the control signal source 11 and outputs a negative control signal _c1 . 21 is a comparator that compares the input signal Vi and the control signal V _c1 and outputs a high level "1" only when Vi>V _c1 ; 22 is the input signal Vi
This is a comparator that compares the control signal _c1 with the inverted control signal c1 and outputs a high level "1" only when Vi< _c1 . 23 is an OR circuit for controlling the opening and closing of the gate circuit 16 by ORing the outputs of the comparators 21 and 22.

In this embodiment, a triangular wave sound source signal is input to the input terminal 18 as the input signal Vi, and in the control signal sources 11 and 12, the DC voltage from the variable resistors VR ₁ and VR ₂ is applied to the control signal V _c1 as shown in the figure. , V _c2 will be described with reference to FIG.

In this case, the relationship between the input signal Vi, the control signal V _c1 and its inverted signal _c1 is as shown in FIG. 7A. The output of the comparator 21 becomes as shown in FIG. 7B, and the output of the comparator 22 as shown in FIG. 7C.

Therefore, the output of the OR circuit 23 becomes "1" near the peaks and valleys of the input signal Vi, as shown in FIG. 7D. Since the gate circuit 16 opens only when the output ○D of the OR circuit 23 is "1" and allows the control signal _Vc2 to pass through, its output signal _Vg is interrupted as shown in FIG. 7D. It becomes a signal.

The arithmetic circuit 17 multiplies the input signal Vi and the gate output Vg in the section where the gate output Vg exists to produce an output signal with a waveform as shown by the solid line in FIG.
Vo is output to the output terminal 19. Also, the input signal Vi
When adding the gate output Vg and the output signal
The waveform of Vo differs only in the portion shown by the broken line in FIG. 7E.

In this embodiment as well, the signal level suddenly changes near the peak of the triangular wave as the input signal, resulting in a complex waveform, and the amount of change and the width of the changing portion depend on the levels of the control signals V _c1 and V _c2 . Therefore, it can be changed arbitrarily. Furthermore, if low frequency signals from the low frequency oscillators 13 and 14 are used as the control signals V _c1 and V _c2 , the output signal waveform can be changed periodically, and if an envelope waveform is used, the tone can be changed according to the envelope waveform when a key is pressed. What can be changed is the same as in the previous embodiment.

Note that the input signal Vi may be any signal whose level changes continuously at a period corresponding to the pitch frequency, such as a sawtooth wave, a triangular wave, or a sine wave. Furthermore, in each of the above-mentioned embodiments, the case where a multiplication or addition circuit was used as the arithmetic circuit 17 was explained.
Of course, similar effects can be obtained by using a subtraction or division circuit.

As explained above, according to the sound source waveform conversion circuit of this invention, a complex waveform can be obtained with a simple configuration. For example, by using this in place of the pulse width modulation circuit 3 of an electronic musical instrument shown in FIG. 1, or by converting the sound source signal waveform of a normal electronic organ whose musical tone output is opened and closed by an on/off switch, It is possible to generate musical tones with rich and varied tones, further enhancing the appeal of electronic musical instruments.

[Brief explanation of the drawing]

Fig. 1 is a block configuration diagram showing an example of a conventional electronic musical instrument, Fig. 2 A and B are signal waveform diagrams for explaining the operation of the pulse width modulation circuit in the electronic musical instrument shown in Fig. A block circuit diagram showing one embodiment of the invention, Figures 4A to 4D are signal waveform diagrams for explaining its operation, Figure 5 is a waveform diagram showing an example of an envelope waveform, and Figure 6 is a diagram showing an example of the envelope waveform. A block circuit diagram showing another embodiment, and FIGS. 7A to 7E are signal waveform diagrams for explaining its operation. 11, 12... Control signal source, 13, 14... Low frequency oscillator, 15, 21, 22... Comparator, 16
...Gate circuit, 17...Arithmetic circuit, 23...
OR circuit, Vi...input signal, Vo...output signal, V
_c1 V _c2 ... Control signal.

Claims (1)

[Claims for Utility Model Registration] 1. A control signal for changing the waveform of a sound source signal whose level changes at a period corresponding to the pitch frequency, each at a constant level or at a time relationship longer than the period of the sound source signal. a control signal source that generates a first control signal and a second control signal whose levels change over time; a comparator that compares the level of the sound source signal and the first control signal; a gate circuit that intermittently outputs the second control signal based on the comparison output of the comparator; 1. A sound source waveform conversion circuit for an electronic musical instrument, comprising an arithmetic circuit that changes the level or rate of change of a signal. 2. The sound source waveform conversion circuit for an electronic musical instrument according to claim 1, wherein the control signal source outputs one control signal as a first control signal and a second control signal.