JPS6255794B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention generates a waveform using a digital circuit, and particularly relates to a musical tone generating device for an electronic musical instrument in which a resonance effect is controlled by a modulation signal that changes over time.

With the advancement of digital technology, it has become possible to generate waveform data using a digital circuit, convert the digital waveform data into an analog signal using a digital-to-analog converter, and generate an analog signal waveform. Waveform generation using such digital circuits is also used in electronic musical instruments, and electronic musical instruments capable of generating waveforms of various tones have been commercialized.

Conventionally, as musical sound generation methods for electronic musical instruments using digital circuits as described above, there are (a) a sine wave synthesis method, (b) a variable filter method, (c) a waveform memory read method, and (d) a frequency modulation method.

The above-mentioned sine wave synthesis method (a) is a method in which a fundamental wave and harmonic sine wave signals are generated by a digital circuit, and the digital waveform signals are synthesized to generate a musical tone with a desired timbre. This method requires channels for calculating the number of types of overtones required in order to obtain a musical tone with a desired overtone composition. Furthermore, when changing the spectrum over time, harmonic control signals for the number of types of overtones are required to vary the amplitude level for each overtone. This method has the problem that the above-mentioned calculation channel and the harmonic control signal require circuits for the number of types of overtones, so the generation circuit becomes large and the generation control of the harmonic control signal becomes complicated. In addition, as an improved type of the sine wave synthesis method of (a), Japanese Patent Application Laid-open No. 1987-48791,
There is a technique disclosed in Japanese Patent Application Laid-Open No. 57-48792. In this prior art, a time window function signal is multiplied by a predetermined partial tone signal, thereby making it possible to easily obtain a large number of higher-order harmonics. However, this prior art
This is just an advanced form of the sine wave synthesis method, and it does not mean that a single waveform signal represents the sound source signal.Furthermore, as described later, as in the present invention, the sine wave synthesis method does not represent the sound source signal. There is also no disclosure of a technique for temporally changing the number of included waveforms.

The variable filter method (b) uses a digital filter, and is a method in which the frequency characteristics of the filter are changed by a variable signal. This method has the problem that the digital filter circuit becomes large. Furthermore, when a waveform is generated at a fixed sampling rate, that is, when the original sound that is input to a digital filter is generated at a fixed sampling rate, it is difficult to obtain a waveform that has many harmonics, and as a result, it is difficult to obtain a waveform that has many harmonics. The problem is that the effectiveness is halved. Furthermore, this method has the problem of generating aliasing distortion.

The waveform memory reading method (c) is a method of generating waveforms by sequentially reading out waveform data stored in a memory or the like in advance in accordance with the phase angle.
Since the waveform data stored in the aforementioned waveform memory is data of a musical waveform generated as a musical tone, the spectrum of the waveform is fixed. Therefore, in order to change the spectrum, waveform data corresponding to the change in the spectrum must be stored in a memory, and furthermore, a control circuit is required to sequentially read out the data in response to the change in the spectrum. Therefore, this method has the problem that the memory capacity increases and the control circuit becomes complicated.

The method (d) applies frequency modulation,
This method uses a carrier wave and a modulating wave, that is, two sine waves, to change the overtones by changing the frequency ratio and modulation depth. Although this method allows overtones to be controlled to some extent, each harmonic changes like a Betzel function, making it difficult to obtain musical tones in which the spectrum envelope changes smoothly.
For example, Japanese Patent Laid-Open No. 54-96017 discloses this type of technology.

Furthermore, there is a method in which a musical sound waveform has a peak (hereinafter referred to as a formant peak) in the high frequency region of the spectrum and changes the musical tone by changing the formant peak frequency over time.
For example, one that uses the resonance effect of a voltage control filter VCF in an analog synthesizer is an example. As a method of generating the above-mentioned formant peak using a digital circuit, (a) the coefficients of the harmonics of the additive synthesis of sine waves are changed over time to generate a filter effect, and the peak occurs at the amplitude value of the harmonic of a higher order. (b) A method of generating a resonance effect similar to that of an analog filter using a digital low-pass filter. Method (a) is the same as method (b) above,
In order to generate harmonics, calculation channels corresponding to higher-order frequencies are required, and amplitude settings are also required for each harmonic, that is, overtones.
The circuit was complicated and difficult to manufacture.
In addition, the method (b) requires a large digital filter circuit and is similarly difficult to implement.

The present invention has been made based on the above-mentioned background, and it generates a musical tone that has a peak in the high frequency region of the spectrum, that is, the high-order harmonic, and uses a resonance effect that changes the harmonic order at which the peak occurs over time. An object of the present invention is to provide a musical tone generator for an electronic musical instrument that can realize the following.

That is, in the present invention, a modulation signal is generated from a modulation signal generating means as a signal whose content changes with time, and this modulation signal is multiplied by an address signal, so that while the address signal specifies an address for one cycle of the waveform, , the modifying means generates a modified address signal specifying an address for more cycles than one cycle of the waveform, the waveform information is read from the storage means using this modified address signal, and after that, the waveform information is
The envelope signal obtained from the address signal is added, and the number of cycles of the waveform included in the envelope signal changes over time as the content of the modulated signal changes over time. It is characterized by being made to do.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 1 is a circuit diagram of an embodiment of the present invention.
FIG. 1 shows an embodiment in which the present invention is applied to an electronic musical instrument. The first output of the keyboard 1 is the frequency information generation circuit 2
Then, the second output is input to a harmonic control signal generation circuit 4 and an envelope control signal generation circuit 5. The output of the frequency information generation circuit 2 is applied to a first input terminal of the phase angle calculation circuit 3. The output of the phase angle calculation circuit 3 is connected to its second input terminal and to the input terminal A of the waveform synthesis circuit 8. The output of the harmonic control signal generation circuit 4 is connected to a first input terminal of the adder circuit 6. A control signal from another circuit (not shown) is input to the second input terminal of the adder circuit 6. Addition circuit 6
The output is input to input terminal B of the waveform synthesis circuit 8. The output terminal C of the waveform synthesis circuit 8 is connected to the first input terminal of the envelope multiplication circuit 7, and the output terminal of the envelope control signal generation circuit 5 is connected to the second input terminal. The output terminal of the envelope multiplication circuit 7 is connected to a digital-to-analog conversion circuit DAC (not shown). The keyboard 1 is a circuit that generates position information of a pressed key and a timing signal of a pressed key.The key position information is sent to a frequency information generation circuit 2, and the key timing signal is sent to a harmonic control signal generation circuit 4. The signals are respectively input to the envelope control signal generation circuit 5. The frequency information generating circuit 2 is a circuit that generates frequency information, that is, phase angle information, corresponding to the pressed key from the position information of the pressed key, and sequentially outputs the phase angle information using, for example, a specific clock. The phase angle calculation circuit 3 is the first
The information applied to the input terminal and the second input terminal are added and output. Since the output of the phase angle calculation circuit 3 is applied to the second input terminal of the phase angle calculation circuit 3,
The phase angle information generated by the frequency information generating circuit 2 is sequentially added to the contents of the phase angle calculating circuit 3 using a specific clock. That is, the phase angle calculation circuit 3
The phase angle information generated by the frequency information generating circuit 2 is accumulated. The accumulation is done in units of one period, and if the phase angle is more than one period, 1
The phase of the period is subtracted. In the embodiment shown in Fig. 1, for example, 2 ¹² is the phase angle of one period (corresponding to 2π), and when the value exceeds that value, a carry is output, but that carry is not used. , the result is one period's worth of phase angle subtracted. The output of the phase angle calculation circuit 3 is input to the input terminal A of the waveform synthesis circuit 8. The timing signal is input to the harmonic control signal generating circuit 4, and is converted by the harmonic control signal generating circuit 4 into a tone control signal for changing the harmonic component over time, for example. The output, that is, the timbre control signal, is added in an adder circuit 6 to an external control signal, for example, a control signal for changing the timbre by an external operator. The adder circuit 6 can be omitted if no control signal is input from the outside. The output of the adder circuit 6 is applied to the input terminal B of the waveform synthesis circuit 8. The waveform synthesis circuit 8 accesses the waveform by obtaining a modified address signal that specifies one period or more while the phase angle, that is, the address signal that changes at a uniform rate inputted from the input terminal A, specifies one period. The degree of control changes depending on the control signal input from input terminal B.

For example, the waveform synthesis circuit 8 includes multiplication circuits 9 and 12, a waveform memory 10, and an envelope generator 11, as shown in FIG. The phase angle input from input terminal A is input to multiplier circuit 9. Further, a timbre control signal, that is, a harmonic control signal, is inputted from input terminal B, and is multiplied by the multiplication circuit 9, and the result, that is, the output of the multiplication circuit 9, accesses the address of the waveform memory 10. The waveform memory 10 specified by the output of the multiplication circuit 9 outputs a waveform value. The output is input to the multiplication circuit 12. On the other hand, the phase angle input from input terminal A is also input to envelope generator 11 . The envelope generator 11 outputs an envelope signal corresponding to the input phase angle. The envelope signal output from the envelope generator 11 is a signal that changes the amplitude value in the waveform memory 10 within one cycle, and is input to the multiplication circuit 12. The output of the waveform memory 10 is input to a multiplication circuit 12, where it is multiplied by the aforementioned envelope signal and output to an output terminal C.

The timing signal of the keyboard 1 is further input to an envelope control signal generation circuit 5. The envelope control signal generation circuit 5 generates control data for changing the amplitude of the musical tone to be output. The output, ie, the envelope signal, is input to an envelope multiplier circuit 7. On the other hand, the waveform data output from the output terminal C of the waveform synthesis circuit 8 is transmitted to the envelope multiplication circuit 7.
The envelope multiplication circuit 7 multiplies the waveform data and the envelope signal and outputs the result. The output of the envelope multiplication circuit 7 is a digital-to-analog conversion circuit DAC (not shown).
input and converted to an analog signal. Note that the envelope multiplication circuit 7 in FIG. 1 is a circuit for changing the envelope over a range of one cycle or more of the waveform, and the multiplication circuit 1 in FIG.
2 is a circuit for changing the amplitude value within one cycle.

That is, the present invention corrects the phase angle in the multiplication circuit 9 as shown in FIG.
This changes the waveform value generated.

FIG. 3 is a first circuit diagram showing in more detail the configuration of the waveform synthesis circuit according to the embodiment of the present invention shown in FIG. Input terminals N, that is, N ₀ -N ₁₁ are connected to inputs A ₀ -A ₁₁ of the multiplier circuit MPY1. Furthermore, the input terminal M is connected to inputs B ₀ to _{B 11} of the multiplier circuit MPY1. Outputs Q ₀ -Q ₇ of the multiplier circuit MPY1 are connected to address inputs A ₀ -A ₇ of the waveform memory ROM.
Its outputs O ₀ ~ O ₇ are the inputs B ₀ ~ B ₇ of the multiplier circuit MPY2.
Enter. On the other hand, terminals N ₄ to _{N 11} are connected to the inverter I ₀
~ _I7 to the inputs _A0 ~ _A7 of the multiplier circuit MPY2. The outputs Q ₀ to Q ₇ are outputted from the output terminal C. Note that the input terminal N corresponds to the input terminal A and the input terminal M corresponds to the input terminal B in FIG. 2, respectively. That is, the input terminal N receives the output of the phase angle calculation circuit 3 shown in FIG. 1, for example, 12-bit phase angle data _N0 to _N11 , and the input terminal M receives the
For example, 12-bit data from adder circuit 6 in the figure
_M0 to _M11 are input.

The value inputted from the input terminal N, that is, the phase angle address value NX, is multiplied by the modulation depth information MX inputted from the input terminal M by the multiplier circuit MPY1. The multiplication circuit MPY1 has a 12-bit multiplication function and performs the calculation (input data of A ₀ to A ₁₁ )×(input data of B ₀ to B ₁₁ )÷ ²¹² . That is, NX×MX÷
2 ¹² is performed, and the lower 8 bits of the operation result Q ₀ ~
Q ₇ is input to addresses A ₀ to _{A 7} of the waveform memory ROM. The waveform memory ROM stores one cycle of a cosine waveform, and its amplitude value consists of 8 bits. That is, since the address of the waveform memory ROM is accessed by changing variously depending on the modulation depth information MX input from the input terminal M in the multiplier circuit MPY1, the amplitude data O ₀ ~ output from the output terminal of the waveform memory ROM O ₇ has its time axis modulated depth information
The value changes depending on MX. Furthermore, the output is input to the multiplication circuit MPY2, and multiplied by the inverted value of the values of bits _N5 to _N11 of the data input from the input terminal N. The multiplier circuit MPY2 performs 8-bit multiplication, which is (input data of A ₀ to A ₇ )×(input data of B ₀ to B ₇ )÷ ²⁸ . This multiplier circuit MPY2 then changes the amplitude value according to the phase angle address value NX. Outputs Q ₀ to _{Q 7} of the multiplier circuit MPY2 are outputted from the output terminal C. The envelope generating device 11 in FIG. 2 corresponds to the inverters I ₀ to I ₇ in FIG. 3.

4 to 7 are waveform diagrams showing output waveforms of each circuit based on modulation depth information MX. a is the phase angle address value NX, b is the output Q of the multiplier circuit MPY1
, c indicates the output of the waveform memory ROM, d indicates the input data values of A ₀ to _{A 7} of the multiplication circuit MPY2, and e indicates the output of the multiplication circuit MPY2, that is, the waveform data value output from the output terminal C. Also, the fourth
The modulation depth information MX in Figures to Figures 7 is “FF” (255), “17F” (383), and “3FF”, respectively.
(1023), “FFF” (4095). here""
indicates hexadecimal display, and ( ) indicates decimal display.

In FIG. 4, one period of the waveforms a and b is the same, and there is no phase change, or in other words, no change in the time axis. As a result, the waveform output from the waveform memory ROM storing the cosine wave is 1
It becomes a periodic cosine wave c. The aforementioned waveform c and waveform d are input to the multiplier circuit MPY2. The waveform d is an inverted value by removing the lower bits (N ₀ - N ₃ ) of the phase angle address value NX by inverters I ₀ - I ₇ , and the waveform is inverted with respect to the modulation depth information MX. This is a waveform with the time axis reversed. Since the waveforms c and d are multiplied by the multiplier circuit MPY2, the output becomes e. FIG. 4 shows a case where only the amplitude value changes in response to phase, that is, time.

In Figures 5 to 7, modulation depth information MX is “FF”
In this case, the address value for accessing the waveform memory ROM is repeated multiple times as shown in b. The same address is accessed 1.5 times in FIG. 5, 4 times in FIG. 6, and 16 times in FIG. 7 during one cycle. This allows waveform memory ROM
The frequency of the waveform output from is 1.5 times, 4 times, 16
It will be doubled. Further, since the amplitude of this waveform is changed corresponding to one period of the modulation depth information MX, the output becomes e. Waveform memory ROM in Figure 5
The output of is starting again from 0 at a certain value of amplitude. Therefore, this waveform becomes discontinuous, but
Since the amplitude value at that time in the multiplier circuit MPY2 becomes zero, unnecessary harmonics are removed. In this way, the frequency spectrum of the waveform output from the multiplier circuit MPY2 is 1.5 times the fundamental frequency and 4 times the fundamental frequency.
Frequencies that are 16x or 16x are emphasized.

FIG. 8 is a circuit diagram in the case where the envelope generating device 11 in FIG. 2 is configured with an exclusive logical OR. To avoid duplication of explanation, we will not explain the same parts as in Figure 3, but the bits input from input terminal N.
N ₃ -N ₁₀ are applied to the first inputs of exclusive logic ORs EOR ₀ -EOR ₇ . Furthermore, bit _N11 is applied to the second input of exclusive logic ORs _EOR1 - _EOR7 . In the case of FIG. 3 described above, the values are applied to the inputs A ₀ to _{A 7} of the multiplier circuit MPY2 in a proportional relationship with the input phase angle address value NX, but in the case of FIG. One cycle becomes a triangular wave and is applied to the multiplier circuit MPY2.

FIG. 9 is a waveform diagram of each circuit generated by the embodiment of FIG. 8. As in Figures 4 to 7, a represents the phase angle address value NX, b represents the output of the multiplier circuit MPY1, c represents the output of the waveform memory ROM, and d represents the inputs of A ₀ to _{A 7} of the multiplier circuit MPY2. The data value and e indicate the output of the multiplier circuit MPY2, respectively. In addition,
The modulation depth information MX at this time is “FFF” (4095)
It is. Therefore, as in Fig. 7, the waveform memory
The address value for accessing the ROM is repeated multiple times, and the same address is accessed 16 times in one cycle. In other words, the waveform output of the waveform memory ROM has a frequency 16 times higher. Further, since the amplitude of this waveform is multiplied by the output data of the exclusive ORs EOR ₁ to EOR ₇ , that is, the triangular waveform, the output becomes e.
Therefore, as in FIG. 7, the frequency 16 times the fundamental frequency is emphasized, but the content of harmonic components is different from that in FIG.

FIG. 10 shows the envelope generator 11 in FIG.
FIG. 3 is a circuit diagram when the waveform memory is configured.
The same parts as in FIG. 3 will not be explained to avoid duplication of explanation, but bits N _{4 to 4} input from input terminal N
Envelope memory where N ₁₁ stores envelope data
Add to HROM address. Its output is applied to inputs A ₀ to _{A 7} of multiplier circuit MPY2. For example, if the envelope waveform stored in the envelope memory HROM is a cosine wave, the amplitude value of the waveform changes in a cosine wave pattern corresponding to one cycle. Furthermore, if the modulation depth information MX is much larger than "FF", for example "FFF", one cycle will have an output waveform as shown in FIG. In FIG. 11, the horizontal axis represents time t, and the vertical axis represents amplitude. Note that the waveform stored in the envelope memory HROM is the waveform memory.
Since it is the same as the cosine wave stored in the ROM, it is also possible to use one memory by sharing the waveform memory ROM or envelope memory HROM by time sharing.

On the other hand, the waveform stored in the envelope memory HROM is not necessarily a cosine wave; for example, if an inverted value of address input or a triangular wave is stored, the operating waveform will be the same as in Figures 3 and 8. become,
The output has the waveform shown in e in each of FIGS. 4 to 7 and 9.

12 to 14 are waveforms A ₁ generated by the embodiments shown in FIGS. 3, 8, and 10.
It is a diagram showing ~F ₁ and its spectrum A ₂ ~F ₂ . In each figure, A _{1 and} A ₂ are when the modulation depth information MX is “FF”, and B ₁ , B ₂ to _{F 1} and F ₂ are when the modulation depth information MX is 1.5 times “FF” and 2 double, quadruple,
This is the case when the magnification is 8 times and 16 times. As is clear from each spectrum, there is a peak value in the second-order fundamental wave component at 2x, and 4x, 8x, and 16x, respectively.
It almost has the peaks of the 2nd, 8th, and 16th harmonics. Therefore, this embodiment makes it possible to obtain a so-called resonance effect.

In the embodiment of the present invention, a multiplier circuit MPY1 is used to change the phase angle. This is possible not only with multipliers but also with dividers, bit shift circuits, etc., for example. Furthermore, the envelope generator 11 shown in FIG. 2 is not limited to inverters I ₀ to I ₇ , exclusive ORs EOR ₀ to EOR ₇ , and envelope memory HROM, but may also be a circuit with other arithmetic functions or a bit shift circuit. It is possible. Furthermore, by temporally changing the modulation depth signal, a signal whose waveform changes over time can be obtained. Therefore,
A waveform in which the harmonic components change with time can be obtained very easily, and the harmonic components with resonance change with time.

As described above, according to the present invention, it is possible to generate a musical tone having a peak at a specific harmonic of the spectrum of a musical waveform. Furthermore, the peak position of this harmonic can be changed over time by the modulation signal, and an effect in which the resonance effect in an analog music synthesizer is changed over time can be easily realized.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a block diagram of the waveform synthesis circuit in Fig. 1, and Figs. 3, 8, and 10 are detailed circuit diagrams of the block diagram in Fig. 2. Figures 4 to 7, 9, and 11 are waveform diagrams of the embodiments of the present invention, and Figures 12 to 14 are waveform diagrams of the embodiments of the present invention when the modulation depth is changed. A spectrum diagram and a waveform diagram are shown respectively. 2... Frequency information generation circuit, 3... Phase angle calculation circuit, 4... Harmonic control signal generation circuit, 5... Envelope control signal generation circuit, 6... Addition circuit,
7... Envelope multiplication circuit, 8... Waveform synthesis circuit, 9, 12... Multiplication circuit, 10... Waveform memory, 11... Envelope generator, MPY1, MPY2
...Multiplication circuit, _I0 to _I7 ...Inverter, ROM...
Waveform memory, EOR ₀ to EOR ₇ ...Exclusive logical OR, HROM...Envelope memory.

Claims (1)

[Scope of Claims] 1. Storage means for storing waveform information; Address signal generation means for sequentially generating address signals for reading out the waveform information stored in the storage means; a modulation signal for modulating the address step speed when addressing and reading the waveform information with the address signal;
A modulated signal generating means that generates a signal whose content changes with the passage of time, and the address signal outputted by the address signal generating means is multiplied by the modulated signal outputted by the modulated signal generating means. While the signal specifies the address of one period of the waveform,
modifying means for obtaining a modified address signal specifying an address for more cycles than one cycle of the waveform; access means for accessing the storage means with the modified address signal generated from the modifying means; and the address signal generating means. an envelope signal generating means for generating an envelope signal from the address signal outputted by the address signal; and adding the envelope signal generated by the envelope signal generating means to the waveform information obtained by querying from the storage means. and additional means, so that the number of cycles of the waveform included in the envelope signal changes over time in accordance with changes in the content of the modulation signal generated by the modulation signal generation means over time. A musical tone generator for an electronic musical instrument, characterized in that: 2. The musical tone generating device for an electronic musical instrument according to claim 1, wherein the envelope signal generating means comprises an inverter that inverts the address signal. 3. The envelope signal generating means receives the most significant bit signal of the address signal as one input,
2. The musical tone generating device for an electronic musical instrument according to claim 1, further comprising a plurality of exclusive logical OR gates whose other inputs are respective bit signals other than the most significant bit of the address signal. 4. The musical tone generating device for an electronic musical instrument according to claim 1, wherein the envelope signal generating means includes a waveform memory addressed by the address signal. 5. The musical tone generation device for an electronic musical instrument according to any one of claims 1 to 4, wherein the adding means includes a multiplication circuit that multiplies the waveform information and the envelope signal. . 6. Any one of claims 1 to 4, wherein the address signal generating means outputs phase angle information specifying a phase angle of a waveform at a uniform rate over one period of the waveform as the address signal. A musical tone generator for an electronic musical instrument according to claim 1. 7. The musical tone generating device for an electronic musical instrument according to any one of claims 1 to 4, wherein the storage means stores a sine wave or a cosine wave as the waveform information.