JP2746068B2 - Modulation signal generator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal generator, and more particularly to a modulated signal generator for performing modulation in an electronic musical instrument, an effector or the like.

[0002]

2. Description of the Related Art In a natural musical instrument, various sound effects such as vibrato and tremolo can be produced by various playing techniques. In an electronic musical instrument as well, a similar sound effect can be realized by modulating an electrically generated tone signal.

A tone signal generated by an electronic musical instrument is subjected to various modulations such as tone color modulation, pitch modulation, and volume modulation using an effector or the like. The effector uses an LFO to add a modulation effect to the electrical tone signal.
(Low frequency oscillator) or the like is used.

The LFO outputs a low-frequency oscillation waveform, and by periodically changing the timbre, volume or pitch,
Modulates the tone signal. If you change the tone periodically,
The effect of the wah is obtained, and for example, it is possible to alternately brighten or darken the tone. If the volume is changed periodically, a tremolo effect is obtained, and the volume can be alternately increased or decreased. If the pitch is changed periodically, a vibrato effect can be obtained, and the pitch can be alternately increased or decreased.

As described above, various modulations change the tone parameters based on the output waveform of the LFO. Then, when trying to change the modulation, the output of the LFO is a sine wave,
A plurality of waveform shapes such as a rectangular wave and a triangular wave are used, and the modulation effect can be changed by properly using these waveforms.
For example, in the case of a triangular wave, the rate of increase and decrease is performed at a constant rate, whereas in the case of a sine wave, the rate of increase and decrease is not constant, and changes rapidly around the phase angle = 0 [rad].
It changes gradually around the phase angle = π / 2 [rad].

[0006]

In the conventional LFO, there is a limit in the variation of the modulation effect, and it cannot always be said that the user's intention can be satisfied.

An object of the present invention is to provide a modulation signal generating apparatus capable of generating a basic signal for performing modulation capable of generating a musical tone with rich expression.

[0008]

SUMMARY OF THE INVENTION A modulated signal generator according to the present invention starts signal generation by a signal generator for generating a periodic signal that changes in accordance with a phase and a signal generator in response to a start instruction signal. A signal generation start unit, a phase comparison unit that compares a predetermined phase signal with the phase of the periodic signal generated by the signal generation unit, and outputs a phase coincidence signal when they match, and a phase coincidence output by the phase comparison unit Signal generation stopping means for stopping signal generation by the signal generation means based on the signal.

[0009]

By setting a predetermined phase angle, the generated signal waveform can be stopped at an arbitrary phase angle, and the phase angle at the start of signal generation and the phase angle at the stop of signal generation can be made different. Can be.

[0010]

FIG. 9 shows an overall configuration example of an electronic musical instrument for implementing the present invention. The keyboard circuit 26 has a plurality of keys for performing music, and outputs signals such as pitch information and key pressing speed by performing operations such as key pressing and key releasing. Further, the keyboard circuit 26 generates and outputs a KONP signal when a key press operation is performed, and generates and outputs a KOFP signal when a key release operation is performed.
KONP signal or KOFP output from keyboard circuit 26
Signals and the like are input to the CPU 21.

The operation unit 25 has a performance operation unit such as a pedal and a slider or a panel operation unit, and is an operation unit for giving an instruction for volume adjustment, tone color selection, or various types of modulation.
The control 25 outputs the control information to the CPU 21.

The CPU 21 receives the KON signal from the keyboard circuit 26.
After inputting the P signal or the like or the control information from the control 25, the calculation is performed and various parameters for tone generation control are output. The CPU 21 outputs a musical tone parameter to the sound source 27, and outputs a DSP (digital signal pr).
The modulation parameter is output to the processor 28. Here, the tone parameters include pitch information, volume information, and the like,
The modulation parameters include an initial phase at the start of modulation and the like.

The program memory 24 stores an operation program. The CPU 21 performs various arithmetic processes using a working memory such as a register and a buffer memory provided in the work memory 23 according to the arithmetic program. The parameter memory 22 stores parameters necessary for generating tone parameters and modulation parameters, and the CPU 21 calculates and outputs tone parameters and modulation parameters based on these parameters.

The tone generator 27 forms and outputs a tone signal required for sound generation based on tone parameters supplied from the CPU 21. The output tone signal is input to the DSP 28, where the DSP 28 performs various types of modulation. DS
P28 has an LFO (Low Frequency Oscillator) 30 and LFO3
Pitch modulation, amplitude modulation, modulation of a filter cutoff frequency, and the like are performed using the oscillation waveform generated and output by 0.

The modulated tone signal is supplied to the DSP 28
Is supplied to the sound system 29, and a musical tone is generated in the sound system 29. The case where the digital tone signal from the sound source 27 is input to the DSP 28 has been described above. If the analog tone signal is to be variously modulated, the analog tone signal is converted into the A / D converter 3.
1 and outputs an output signal from the A / D converter 31 to the DSP
28. In the A / D converter 31, the tone signal converted into a digital signal is input to the DSP 28, where the tone signal is modulated.

FIG. 1 is a block circuit diagram of an LFO according to an embodiment of the present invention. The LFO is the DSP 28 shown in FIG.
And an oscillator for performing various types of modulation. Modulation parameter signals for the initial phase, final phase, frequency data, and number of repetitions are generated in the CPU and supplied to the LFO. The initial phase signal is input to the latch L3 and latched. Similarly, the final phase signal, frequency data signal, and repetition count signal are input to and latched by the latches L2, L4, and L1, respectively.

The frequency data signal stored in the latch L4 is input to the AND gate 4. AND gate 4
Has a frequency data signal and a flip-flop 9 (FF)
Is input. When the input signal from the flip-flop 9 is "1", the AND gate 4 passes and outputs the frequency data signal. Conversely, flip-flop 9
Is "0", the AND gate 4 does not pass the frequency data signal and outputs the signal "0".

Here, the operation of the flip-flop 9 will be described. The flip-flop 9 has two inputs and one output, and inputs are a KONP signal or a KOFP signal and an output signal from the comparison circuit 7 (CMP2). The KONP signal and the KOFP signal are signals emitted when a key is pressed and released, respectively, and are input from the keyboard circuit to the LFO via the CPU. The flip-flop 9 is an RS flip-flop.

FIG. 2 shows a truth table of the RS flip-flop. The KONP / KOFP signal and the comparison circuit (CMP) are shown.
A signal state of the two inputs of the output signal of 2) represents the output signal Q _n at that time the flip-flop. KONP / KOFP
The signal corresponds to the set signal, and the output signal of the comparison circuit (CMP2) corresponds to the reset signal.

When the KONP / KOFP signal is "0",
When the output signal of the comparison circuit (CMP2) is "0", the flip-flop keeps holding the previous output signal Qn _-1 . When the KONP / KOFP signal is “1” and the output signal of the comparison circuit (CMP2) is “0”, the flip-flop outputs a signal “1”. KONP / K
When the OFP signal is “0” and the output signal of the comparison circuit (CMP2) is “1”, the flip-flop outputs a signal “0”. When the KONP / KOFP signal is “1” and the output signal of the comparison circuit (CMP2) is “1”, the output of the flip-flop is undefined.

The operation of the flip-flop 9 in FIG. 1 will be described. In a steady state in which no keyboard operation is performed, a signal “0” is output from the comparison circuit 7 (CMP2).
Then, the KONP / KOFP signal is also “0”. The output of the flip-flop 9 keeps holding the signal “0” reset in the initial setting. Therefore, the AND gate 4 receiving the output signal of the flip-flop 9 as an input
Does not output a frequency data signal.

When a key is pressed in the keyboard circuit, KONP
The signal is input to flip-flop 9, and flip-flop 9 outputs signal "1". Thereby, the AND gate 4 outputs the frequency data signal stored in the latch L4.

The output frequency data signal is stored in accumulator 1
And accumulates frequency data. The accumulator 1
An adder circuit 2 and a delay circuit 3 are provided. AND gate 4
Is output to the adder circuit 2. The output signal of the adding circuit 2 is input to the delay circuit 3 and is delayed by a predetermined unit time. The signal output from the delay circuit 3 is fed back, input to the addition circuit 2, and added to the frequency data signal output from the AND gate 4.

When a KONP signal is generated by depressing the key, the AND gate 4 opens to allow the frequency data signal to pass, and at the same time, the KONP signal clears the delay circuit 3 and makes the output of the delay circuit 3 zero. Then, the addition circuit 2 adds the input frequency data signal to 0, and outputs the frequency data signal as it is. The frequency data signal output from the adding circuit 2 is
Is delayed by one data, and then fed back to the addition circuit 2, and at the same time, the delayed signal becomes the output of the accumulation unit 1. Thereafter, the accumulated signal output from the delay circuit 3 sequentially increases by the magnitude of the frequency data signal each time the unit time elapses.

The accumulated signal output from the delay circuit 3 is input to the addition circuit 5, and is added to the initial phase signal stored in the latch L3. Therefore, the delay circuit 3
The accumulated signal output from the above does not start from 0, but starts from an initial phase and is sequentially accumulated. An accumulation signal as a result of the addition represents phase data. The accumulated signal is input to the waveform table circuit 10 and, for example, a sine wave LFO output waveform is formed by performing a lookup from a preset table.

The output waveform of the LFO is stored in a waveform table circuit 1
Determined by the table in 0. Therefore, a sine wave, a rectangular wave, a triangular wave, or the like can be output according to the set table.

FIG. 4 shows the waveform table circuit 10 shown in FIG.
Shows the waveforms input to. An example in which the addition circuit in the LFO is an adder having a 4-bit width output will be described. As an input signal to the LFO, an initial phase = φ1,
It is assumed that final phase = φ2 and frequency data = φ0 are set. The abscissa indicates the passage of time, and the ordinate indicates the 4-bit length of the accumulated signal input to the waveform table circuit. The accumulated signal represents the phase, and the accumulated signal “0000” is 0
[Rad], and the accumulated signal “1111” is 2π [ra].
d].

The time when the KONP signal is generated by the key depression is defined as t0. The accumulated signal at time t0 has the initial phase φ1. After a lapse of the unit time (t1-t0), the frequency data φ0 is added to the initial phase φ1 at time t1.
Is formed as an accumulated signal (φ1 + φ0). Thereafter, every time the unit time (t1-t0) elapses, the frequency data φ0
Are accumulated.

When the time t3 is reached, the accumulated signal "111"
For "1", further accumulation is performed. Here, the addition circuit is 4
Because of the bit output, the adder circuit originally generates an overflow or carry signal. However, they are ignored and adding 1 to the signal “1111” results in the signal “000”.
It has the function of an addition circuit that becomes "0". That is, the signal “1”
After "111", the signal circulates to the signal "0000". In this way, the accumulated signal forms a sawtooth wave.

After the accumulation signal forms a sawtooth wave for a predetermined period indicated by the repetition number signal, the accumulation is stopped when it reaches the final phase φ2. For example, when the number of repetitions is set to 4, an accumulated signal of the initial phase φ1 is obtained at time t0, and reaches the first final phase φ2 at time t2. At time t4, the phase reaches the second final phase φ2, and at time t5, the phase reaches the third final phase φ2. At time t6, the phase reaches the fourth final phase φ2 indicated by the repetition number signal, and thereafter,
The accumulated signal keeps the final phase φ2. Next, a circuit configuration for realizing this function will be described.

In FIG. 1, the comparison circuit 6 (CMP1) receives as input the frequency data accumulation signal obtained by adding the initial phase signal in the addition circuit 5 and the final phase signal stored in the latch L2. The comparison circuit 6 compares the accumulated signal with the final phase signal, and outputs a coincidence signal to the counter circuit 8 if they coincide. Since the accumulated signal input to the comparison circuit 6 forms a sawtooth wave, it coincides with the final phase at one cycle interval. That is, as long as the accumulated signal continues to form the sawtooth wave, the comparison circuit 6 outputs the coincidence signal every one cycle of the sawtooth wave.

The counter circuit 8 counts the number of coincidence signals received from the comparison circuit 6. That is, the number of times the accumulated signal forming the sawtooth wave matches the final phase is counted. The count value is input to the comparison circuit 7 (CMP2), and is compared with the repetition number signal stored in the latch L1. The comparison circuit 7 outputs a coincidence signal when the count value of the counter circuit 8 reaches the predetermined number of repetitions stored in the latch L1.

The coincidence signal generated by the comparison circuit 7 resets the counter circuit 8. When reset, the counter circuit 8 restarts counting from 0. The match signal output from the comparison circuit 7 is input to the flip-flop 9. The output signal of the comparison circuit and the KONP / KOFP signal are input to the flip-flop 9. The flip-flop 9 is connected to the comparison circuit 7 (CMP) as shown in FIG.
If a match signal "1" is input from 2), "0" is output.

Output signal "0" from flip-flop 9
Is input to the AND gate 4. The AND gate 4 closes the gate and does not pass frequency data. As a result, the increase of the accumulation signal output from the accumulation unit 1 is stopped, and the output of a constant value is continued.

FIG. 3 is a timing chart for explaining the circuit operation of the LFO of FIG. The KONP / KOFP signal input to the flip-flop 9 shown in FIG. 1, the output signal of the comparison circuit 7 (CMP2), the output signal of the flip-flop 9 and the output L of the waveform table circuit 10.
5 shows the FO output signal. The case where the initial phase and the final phase input to the LFO are set to π / 2 [rad] and the number of repetitions is set to 6 will be described.

First, a KO is performed by performing a key pressing operation.
An NP signal is generated, and a first pulse signal appears on the KONP / KOFP signal line. Due to the input of the KONP / KOFP signal, the output of the flip-flop goes high. After that, even if the pulse signal of the KONP / KOFP signal falls, the flip-flop keeps the previous state, and thus remains in the high state.

While the flip-flop is in the high state, the accumulated signal input to the waveform table circuit continues to increase, forming a sawtooth wave. The accumulated signal input to the waveform table circuit is converted into, for example, a sine wave and becomes an LFO output.
Here, according to the set initial phase, the LFO output becomes π / 2 [ra] at the same time when the flip-flop becomes high.
The sine wave oscillation is started from the phase of d]. Then, the tone generated when the key is pressed is modulated.

The accumulated signal has a final phase of π / 2 [r
ad], the comparison circuit (CMP2) emits a pulse signal representing a coincidence signal. This match signal is input to the flip-flop, and the output of the flip-flop changes from the high state to the low state. When the output of the flip-flop goes low, the accumulation of the accumulation signal is stopped and the LFO output signal becomes
The sine wave signal in the phase of π / 2 [rad], which is the final phase, is kept, and the oscillation is stopped.

When a key release operation is subsequently performed, a KOFP signal is generated.
A third pulse signal appears. With the input of the pulse signal, the output of the flip-flop changes from a low state to a high state.

When the flip-flop goes high, the accumulated signal input to the waveform table circuit forms a sawtooth wave again. The accumulated signal input to the waveform table circuit is converted into a sine wave, and the oscillation is restarted from the last phase = π / 2 [rad] where the oscillation was stopped last time. Then, the tone generated at the time of key release is modulated.

As for the accumulated signal, the comparator (CMP2) outputs a pulse signal of a coincidence signal after counting the final phase = π / 2 [rad] six times as in the case of the key depression. When the coincidence signal is input to the flip-flop, the output of the flip-flop changes from a high state to a low state. When the flip-flop goes to the low state, the LFO output signal continues to hold the sine wave signal at the final phase = π / 2 [rad] and stops oscillation.

FIG. 5 shows an LFO according to another embodiment of the present invention.
3 is a block circuit diagram of FIG. In the LFO according to the present embodiment,
An initial phase, an intermediate phase, a repetition number 1, a last phase, a repetition number 2, and frequency data are input from outside. The intermediate phase and the number of repetitions 1 are parameters that determine the modulation effect at the time of key depression, and the last phase and the number of repetitions 2 are parameters that determine the modulation effect at the time of key release.

By performing the key pressing operation, the LFO output signal starts oscillating from the signal of the "initial phase", an accumulation signal for accumulating the "frequency data" is formed, and the "intermediate phase" is changed. Oscillation is stopped when the number of repetitions 1 is counted. When the key release operation is performed, the LFO output signal restarts oscillating. When the “last phase” is counted by “the number of repetitions 2”, the oscillation is stopped.

The operation will be described below with reference to the block circuit diagram shown in FIG. The modulation parameter signal of the initial phase, the intermediate phase, the number of repetitions 1, and the frequency data is generated in the CPU, input to the latches L3, L2, L1, L4 and latched.

The frequency data signal stored in the latch L 4 is input to the AND gate 4 together with the output signal from the OR gate 11. The output signal of the flip-flop 9 (FF1) and the flip-flop 15
The output signal of (FF2) is input. Only when the input signal from the OR gate 11 is "1", the AND gate 4 passes and outputs the frequency data signal.

When a key is pressed in the keyboard circuit, KONP
The signal is input to flip-flop 9, and flip-flop 9 outputs signal "1". As a result, the AND gate 4 outputs the frequency data signal stored in the latch L4 and supplies the frequency data signal to the addition circuit 2. The output of the adding circuit 2 is input to the delay circuit 3 and is delayed by a predetermined unit time. The signal output from the delay circuit 3 is fed back, input to the addition circuit 2, and added to the frequency data signal output from the AND gate 4.

When a KONP signal is generated by a key depression operation, the KONP signal clears the delay circuit 3. The accumulated signal, which is the output of the delay circuit 3, sequentially increases by the magnitude of the frequency data signal each time the unit time elapses.
The accumulated signal output from the delay circuit 3 is added to the addition circuit 5
And is added to the initial phase signal stored in the latch L3. The accumulated signal, which is the result of the addition, is input to the waveform table circuit 10, and a lookup is performed from a preset table, thereby forming, for example, a sine wave LFO output waveform.

The comparing circuit 6 (CMP1) includes an adding circuit 5
, The accumulated signal obtained by adding the initial phase signal and the latch L2
Is input. Comparison circuit 6
Compares the accumulated signal with the intermediate phase signal, and outputs a coincidence signal to the counter circuit 8 if they coincide with each other. Since the accumulated signal input to the comparison circuit 6 forms a sawtooth wave, it coincides with an intermediate phase at one cycle interval.

The counter circuit 8 counts the number of coincidence signals received from the comparison circuit 6. That is, the number of times that the accumulated signal forming the sawtooth wave coincides with the middle phase is counted. The count value is input to the comparison circuit 7 (CMP2) and compared with the repetition number 1 signal stored in the latch L1. The comparison circuit 7 outputs a coincidence signal when the count value of the counter circuit 8 reaches the number of repetitions 1 stored in the latch L1.

The coincidence signal generated by the comparison circuit 7 resets the counter circuit 8. When reset, the counter circuit 8 restarts counting from 0. The match signal output from the comparison circuit 7 is input to the flip-flop 9. The output signal of the comparison circuit 7 and the KONP signal are input to the flip-flop 9. When the match signal “1” is input from the comparison circuit 7, the flip-flop 9
The signal "0" is output.

Output signal "0" from flip-flop 9
Is input to the OR gate 11. Until the key release operation is performed, the output signal of the flip-flop 15 is “0”. Therefore, the signal “0” is input to the AND gate 4 via the OR gate 11. As a result, the AND gate 4 closes the gate, does not pass the frequency data, stops increasing the accumulated signal, and continues to output a constant value.

Next, a circuit operation when a key release operation is performed will be described. When a key release operation is performed, a KOFP signal is generated and input to the flip-flop 15. The flip-flop 15 outputs a signal “1”, and the signal “1” is input to the AND gate 4 via the OR gate 11. As a result, the accumulated signal input to the waveform table 10 resumes the accumulation for the frequency data. At the same time, the LFO output resumes oscillation.

The modulation parameter signal having the last phase and the number of repetitions 2 is C
The data is generated in the PU, input to the latches L5 and L6, and latched.

The accumulated signal input to the waveform table circuit 10 and the last phase signal stored in the latch L5 are input to the comparison circuit 12 (CMP3). Comparison circuit 12
Compares the accumulated signal with the last phase signal, and outputs a coincidence signal to the counter circuit 14 if they match.

The counter circuit 14 counts the number of times that the accumulated signal forming the sawtooth wave coincides with the last phase. The count value is input to the comparison circuit 13 (CMP4), and is compared with the repetition number 2 signal stored in the latch L6. The comparison circuit 13 outputs a coincidence signal when the count value of the counter circuit 14 reaches the number of repetitions 2.

The coincidence signal generated by the comparison circuit 13 resets the counter circuit 14. When reset, the counter circuit 14 restarts counting from 0. The match signal output from the comparison circuit 13 is input to the flip-flop 15 (FF2). Flip-flop 1
5, the output signal of the comparison circuit 13 and the KOFP signal are input. The flip-flop 15 outputs a signal “0” when the match signal “1” is input from the comparison circuit 13.

The output signal “0” from the flip-flop 15 is input to the OR gate 11. Until the next key pressing operation is performed, the output signal of the flip-flop 9 is “0”, so the signal “0” is input to the AND gate 4 via the OR gate 11. This allows AND
Gate 4 closes the gate, does not pass frequency data,
The increase of the accumulation signal is stopped, and a constant value is continuously output. Accordingly, the LFO output also stops oscillating and continues to output a constant value.

FIG. 6 is a timing chart for explaining the circuit operation of the LFO of FIG. The relationship between the LFO output waveform for the KONP signal generated when a key is depressed and the KOFP signal generated when a key is released is shown. In order to explain the circuit operation shown in FIG. 5, the output signal of the comparison circuit 7 (CMP2), the output signal of the flip-flop 9 (FF1), the output signal of the comparison circuit 13 (CMP4), and the flip-flop 15 The output signal of (FF2) is also shown.

Here, the modulation parameters externally input to the LFO are as follows: initial phase = π / 2 [rad], intermediate phase = π / 2 [rad], number of repetitions 1 = 6, last phase = 5π / rad It is assumed that 6 [rad] and the number of repetitions 2 = 4 are set.

First, by performing a key pressing operation, a pulse-like KONP signal is generated. By the input of the KONP signal, the output of the flip-flop (FF1) becomes high. While the flip-flop (FF1) is in the high state, the accumulated signal input to the waveform table circuit continues to increase, forming a sawtooth wave. The accumulated signal is input to the waveform table circuit, and the output LFO output starts sine wave oscillation. At this time, according to the set initial phase, LFO
The output starts sine wave oscillation from the phase of π / 2 [rad] as soon as the flip-flop rises to the high state.
Then, the tone generated when the key is pressed is modulated.

When the accumulated signal has an intermediate phase = π / 2 [ra
When d] matches six times, which is the set number of repetitions, the comparison circuit (CMP2) emits a pulse signal representing a match signal. This coincidence signal is supplied to a flip-flop (FF1)
And the output of the flip-flop (FF1) transitions from the high state to the low state. Flip-flop (FF
When the output of 1) goes to a low state, the increase of the accumulated signal is stopped, and the LFO output signal has an intermediate phase = π / 2 [ra].
d), the oscillation is stopped.

Subsequently, when a key release operation is performed, a pulse-like KO
An FP signal is generated. By inputting this KOFP signal,
The output of the flip-flop (FF2) changes from a low state to a high state. When the output of the flip-flop (FF2) goes high, the accumulated signal input to the waveform table circuit forms a sawtooth wave again. The accumulated signal input to the waveform table circuit is converted into a sine wave, and the LFO is shifted from the phase where π / [rad] was stopped last time.
Restarts oscillation. Then, the tone generated at the time of key release is modulated.

The accumulated signal has the last phase = 5π / 6 [ra
After d] is repeated 2 times = 4 times, the comparison circuit (CMP4) outputs a pulse signal of a coincidence signal. When the match signal is input to the flip-flop (FF2), the output of the flip-flop (FF2) changes from the high state to the low state. When the output of the flip-flop (FF2) goes low, the LFO output signal continues to hold the sine wave signal at the last phase = π / 2 [rad],
Stop oscillation.

As described above, by setting the number of repetitions 1 and the number of repetitions 2, the LFO that modulates when the key is pressed is set.
And the oscillation time of the LFO to be modulated at the time of key release can be made different. Also, by setting the middle phase and the last phase, the oscillation stop phase of the LFO that modulates when the key is pressed and the oscillation stop phase of the LFO that modulates when the key is released can be made different.

Next, examples of performing tone color modulation, amplitude modulation and pitch modulation using the LFO will be described. FIG.
FIG. 2 is a block circuit diagram of a DSP that performs tone color modulation by O. By performing LFO modulation on the cutoff frequency of the filter, it is possible to obtain the effect of wah, which is timbre modulation.

The DSP has a low-pass filter 41 and a high-pass filter 42, and constitutes a band-pass filter. The tone signal input to the DSP is input to the low-pass filter 41. Then, the low-pass filter 41
A tone signal having only a frequency component lower than the cutoff frequency of the signal passes through and is input to the high-pass filter 42. The high-pass filter 42 outputs only a tone signal having a higher frequency component than the cutoff frequency, and becomes an output signal of the DSP.

That is, the cutoff frequency of the low pass filter 41 corresponds to the upper limit frequency of the band pass filter, and the cut off frequency of the high pass filter 42 corresponds to the lower limit frequency of the band pass filter. The wah effect is obtained by periodically varying the pass bandwidth of the bandpass filter.

The cut-off characteristic of the low-pass filter 41 is determined by a signal input from the coefficient table circuit 43. Further, the cutoff characteristic of the high-pass filter 42 is determined by a signal input from the coefficient table circuit 44. The coefficient table circuits 43 and 44 perform a table lookup in accordance with the signal input from the LFO, and convert signals representing the cutoff characteristics of the filters into the filters 41 and 4 respectively.
Output to 2.

A case where one LFO for performing modulation and a case where two LFOs are used will be described. First, 1 LFO
When one is used, the oscillation signal of LFO1 is input to the coefficient table circuit 43 and the coefficient table circuit 44. The coefficient table circuit 43 periodically changes the cutoff characteristic of the low-pass filter 41 according to the oscillation signal input from the LFO 1. The coefficient table circuit 44 periodically changes the cutoff characteristic of the high-pass filter 42 according to the oscillation signal input from the LFO 1. Therefore, 2
The characteristics of the two filters 41 and 42 change synchronously.

When two LFOs are used, the oscillation signal of LFO 1 is input to the coefficient table circuit 43, and the oscillation signal of LFO 2 is input to the coefficient table circuit 44. The coefficient table circuit 43 periodically changes the cutoff characteristic of the low-pass filter 41 according to the oscillation signal input from the LFO 1. The coefficient table circuit 44 periodically changes the cutoff characteristic of the high-pass filter 42 according to the oscillation signal input from the LFO 2. Since the two filters 41 and 42 can be independently modulated, complex modulation is possible.

FIG. 8 shows the characteristics of the band-pass filter formed by the DSP program shown in FIG. In the graph shown in the figure, the horizontal axis indicates frequency, and the vertical axis indicates signal magnitude.

FIG. 8A shows band-pass filter characteristics when the cut-off characteristics of the low-pass filter and the high-pass filter are modulated by the same LFO. The source that modulates the cutoff characteristics of the low-pass filter and the high-pass filter is the same LFO1. Therefore, when the upper limit of the pass bandwidth of the bandpass filter changes, the lower limit also changes. This is effective when, for example, the pass bandwidth having the same bandwidth is periodically changed on the frequency axis.

Further, the LFO can arbitrarily set the modulation parameter of the final phase, the middle phase, or the last phase for stopping the modulation. Can be determined.

FIG. 8B shows bandpass filter characteristics when the cutoff characteristics of the lowpass filter and the highpass filter are modulated by different LFOs. The cut-off characteristic of the low-pass filter is modulated by LFO1, and the cut-off characteristic of the high-pass filter is modulated by LFO2.

Since LFO1 and LFO2 can independently generate oscillation waveforms, they can be set to different oscillation frequencies or different waveform shapes. This allows
The changing speed of the filter characteristics of the low-pass filter and the filter characteristics of the high-pass filter can be changed, and the amount of change with time can be changed.

For example, when the LFO1 and the LFO2 form the same waveform having the same oscillation frequency, the upper and lower limits of the pass bandwidth change so as to move in parallel. By setting the final phases of LFO1 and LFO2 respectively,
The cut-off characteristic of the low-pass filter and the cut-off characteristic of the high-pass filter when the modulation is completed can be arbitrarily determined. Therefore, when the modulation is performed by moving the upper and lower limits in parallel with a fixed pass bandwidth, the pass bandwidth can be set wider or narrower when the modulation is completed. When the wah effect is obtained by the modulation and when the modulation is finished, the filter has different filter characteristics, and thus can be used as a filter for tone color adjustment.

By making the modulation parameters for the number of repetitions of LFO1 and LFO2 different, it is possible to provide a difference between the time during which the characteristics of the low-pass filter are modulated and the time during which the characteristics of the high-pass filter are modulated. That is, after the modulation of the upper limit frequency of the passband is completed, it is also possible to continue modulating only the lower limit frequency for a while.

Next, an example in which amplitude modulation is performed using LFO will be described. Pressing a key generates a KONP signal. At the same time, if the amplitude modulation by the LFO is started, the volume changes periodically, and a tremolo effect can be obtained. Then, after the number set as the number of repetitions of the modulation parameter, sound generation is continued at an arbitrary volume corresponding to the final phase. When the key is released, a KOFP signal is generated, and the tremolo effect is obtained again.

Finally, an example in which pitch modulation is performed using an LFO will be described. If pitch modulation by the LFO is started by depressing a key, the pitch changes periodically, and a chorus or vibrato effect can be obtained. The modulation parameter can be made to correspond to the final phase, and all the keys corresponding to the keys can be pitch-changed by a fixed pitch to apply a detune effect. In this way, it is also possible to make the effect different during key depression. When the detune effect is provided, sounds having slightly different pitches are simultaneously generated, so that a wide sound can be obtained.

A case where delay vibrato is realized as an application of vibrato will be described. The KONP signal generated by key depression in the keyboard circuit is input to the CPU. The CPU outputs the KONP signal only to the sound source and not to the DSP. After counting the desired delay time by the timer, the CPU sets the LFO in the DSP to K
What is necessary is just to output an ONP signal. After the musical tone is emitted,
After the elapse of the delay time, a vibrato effect is obtained.

As described above, the output signal of the LFO is used for the modulation as it is. However, if an oscillation signal from the LFO is enveloped using an envelope generator (EG), a finer modulation waveform can be generated. If the modulated signal thus generated is used for various types of modulation, more complicated modulation becomes possible.

The case where the LFO according to the present embodiment is built in the DSP and various types of modulation can be performed by inputting a tone signal to the DSP has been described. It cannot be applied. For example, an LFO can be incorporated in a sound source to modulate a generated tone signal. In addition, in order to control the CPU, each unit can be programmed by a software method to realize LFO.

In this embodiment, the KO generated at the time of key depression is used as a trigger signal when starting or ending the oscillation of the LFO.
Although the case where the NP signal or the KOFP signal generated at the time of key release is used has been described, the trigger signal may be generated by an external operator. By supplying an operator signal generated by operating an external operator to the LFO, the start or end of the LFO can be controlled. If an external operator is used, the start or end of modulation can be instructed at an arbitrary timing according to the user's intention. In addition, since the external operator can be operated a plurality of times while the key is being pressed, the modulation can be turned on and off repeatedly while the tone signal is being generated.

The present invention has been described in connection with the preferred embodiments.
The present invention is not limited to these. For example, it will be apparent to those skilled in the art that various modifications, improvements, combinations, and the like can be made.

[0085]

Since the generated signal waveform can be stopped at an arbitrary phase angle, the signal value after the stop of the signal generation can be specified. For example, the volume and pitch of a musical tone generated after the stop of signal generation can be determined to desired values.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram of an LFO according to an embodiment of the present invention.

FIG. 2 is a truth table of an RS flip-flop.

FIG. 3 is a timing chart for explaining a circuit operation of the LFO of FIG. 1;

FIG. 4 shows a waveform input to the waveform table circuit shown in FIG.

FIG. 5 is a block circuit diagram of an LFO according to another embodiment of the present invention.

FIG. 6 is a timing chart for explaining a circuit operation of the LFO of FIG. 5;

FIG. 7 is a block circuit diagram of a DSP that performs tone color modulation by LFO.

8 shows characteristics of the bandpass filter of the DSP shown in FIG. FIG. 8A shows band-pass filter characteristics when the cutoff characteristics of the low-pass filter and the high-pass filter are modulated by the same LFO, and FIG.
This is a bandpass filter characteristic when the cutoff characteristics of the lowpass filter and the highpass filter are modulated by different LFOs.

FIG. 9 shows an overall configuration example of an electronic musical instrument including an embodiment of the present invention.

[Explanation of symbols]

L latch, 1 accumulator, 2,5 adder,
3 delay circuit, 4 AND gate,
6, 7, 12, 13 Comparison circuit, 8, 14 counter circuit, 9, 15 flip-flop, 10 waveform table circuit, 11 OR gate

Claims (3)

(57) [Claims] 1. A signal generation means (1) for generating a periodic signal that changes according to a phase; a signal generation start means (4) for starting signal generation by the signal generation means in response to a start instruction signal; A phase comparison means (6) for comparing a predetermined phase signal with a phase of the periodic signal generated by the signal generation means and outputting a phase coincidence signal when they coincide with each other; and a phase coincidence signal output by the phase comparison means On the basis of,
A modulated signal generation device having signal generation stopping means (4) for stopping signal generation by the signal generating means. A counting means for counting a phase coincidence signal output from the phase comparing means; a predetermined repetition number signal and a count value counted by the counting means; And a number comparing means (7) for outputting a coincidence signal, wherein the signal generation stopping means stops signal generation by the signal generating means in response to the number of times coincidence signal output by the number comparing means. The modulated signal generator according to any one of the preceding claims. 3. A signal generation / resumption means (4) for restarting signal generation by said signal generation means in response to a restart instruction signal, and comparing another phase signal with the phase of the periodic signal after restarting,
3. A modulation signal generating apparatus according to claim 1, further comprising another phase comparing means for outputting a phase coincidence signal when coincidence occurs.