JP3844214B2 - Modulation waveform generator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a modulation waveform generator applied to an electronic musical instrument or the like.
[0002]
[Prior art]
A special effect is often applied to musical sounds generated by an electronic musical instrument by changing the amplitude, frequency, pan (the volume balance between left and right in a stereo sound), or timbre. In order to give such a special effect, a modulation wave (low frequency) waveform generator, so-called LFO is provided. The period of the special effect for the musical sound is determined by the period of the modulation waveform output from the LFO.
[0003]
On the other hand, many electronic musical instruments in recent years have functions of automatic performance and automatic accompaniment. In automatic performance and automatic accompaniment, the tempo for automatic performance and accompaniment is specified. For example, in automatic performance data expressed by MIDI (Musical Instruments Digital Interface) data, data specifying a tempo is set at the beginning or middle of a song, and the tempo is set at the beginning or middle of the song.
[0004]
If the timing of the tempo on the side of such automatic performance / accompaniment and the timing of the special effect do not match, the musical sound becomes unnatural. Therefore, a technique for synchronizing the LFO that defines the cycle of the special effect and the tempo of automatic performance / accompaniment has been proposed. For example, in Japanese Patent No. 2621669, a first musical sound signal is generated in response to a musical sound signal generation instruction by the instruction means, and a second musical sound signal is automatically generated according to the tempo set by the tempo setting means, Furthermore, an electronic musical instrument is disclosed in which a modulation signal having a period corresponding to the tempo set by the tempo setting means is generated and the first musical tone signal is modulated based on the modulation signal. According to this, the tempo of the second musical sound signal (automatic accompaniment) follows the tempo set by the tempo setting means and further modulates the first musical sound signal with the modulation signal having a period corresponding to the tempo. The period of the signal can correspond to the tempo of automatic accompaniment, and the modulation of the first musical sound signal can be synchronized with the automatic accompaniment. In the following, an LFO that generates a modulation signal having a period synchronized with the tempo of automatic performance or automatic accompaniment is referred to as “tempo synchronization LFO”.
[0005]
[Problems to be solved by the invention]
The one described in the above-mentioned Japanese Patent No. 2621669 generates a modulation signal synchronized with a tempo given as a numerical value, and is a tempo clock that actually defines the tempo (for example, a tempo input as MIDI data). It does not generate a modulation signal synchronized with the clock). In particular, when the time interval of the tempo clock that defines the tempo of automatic performance (hereinafter simply referred to as “automatic performance” includes automatic accompaniment) fluctuates, in the conventional tempo synchronization LFO, the tempo clock whose cycle varies It is difficult to synchronize. Further, in the conventional tempo synchronization LFO, even if a tempo value as a numerical value is supplied together with the tempo clock from the automatic performance means, the tempo change timings cannot be completely matched with each other. Not taken.
[0006]
Further, when the LFO that generates a modulation waveform according to the designated tempo (the LFO in the sound source) is an oscillator independent of the automatic performance means (generally a CPU), even if the tempo value is fixed. There is a problem that the tempo clock and the modulation waveform are gradually shifted with time. Although it is conceivable that the CPU is in charge of tempo-synchronized LFO waveform generation processing, the CPU performs LFO processing for the number of sound generation channels for each sampling period, which is a heavy burden.
[0007]
In view of the above-described problems in the prior art, the present invention provides a modulation waveform generator capable of generating a modulation waveform synchronized with the tempo of automatic performance even when the LFO and the automatic performance means are provided independently. The purpose is to provide.
[0008]
[Means for Solving the Problems]
In order to achieve this object, the invention according to claim 1 is a modulation waveform generator for generating a plurality of modulation waveforms used in a sound source having a plurality of channels for generating musical sounds, wherein a plurality of beats synchronized with the tempo are provided. Predetermined bits that make a round number Basic waveform generating means for generating the basic waveform, storage means for storing a multiplier for each channel of the plurality of channels, and multiplying the basic waveform by a multiplier for each channel, and the multiplication result Of these, the part consisting of the same number of bits as the basic waveform is the multiplication result waveform for each channel. Output multiplication means; The multiplication means outputs Multiplication result for each channel Waveform And modulation waveform generating means for generating a modulation waveform for each channel.
[0009]
The invention according to claim 2 A modulation waveform generator for generating a plurality of modulation waveforms used in a sound source having a plurality of channels for generating musical sounds, and generating a basic waveform having a predetermined number of bits that circulates in a plurality of beats synchronized with the tempo Means, a storage means for storing a multiplier for each channel of the plurality of channels, a multiplier for each channel multiplied by the basic waveform, and a portion of a predetermined number of bits in the multiplication result is assigned to each channel. Multiplication means for outputting as a multiplication result waveform for each channel, and modulation waveform generation means for generating a modulation waveform for each channel based on the multiplication result waveform for each channel output by the multiplication means; It is provided with.
[0010]
The invention according to claim 3 3. The modulation waveform generating apparatus according to claim 1, wherein the basic waveform generating means accumulates a first predetermined value every time a tempo signal generated in synchronization with a tempo is received. Means for accumulating a second predetermined value at a predetermined period shorter than the period of the tempo signal, and outputting a second accumulated value, and when receiving the tempo signal, Coincidence control means for substantially matching the second accumulated value accumulated by the accumulating means with the first accumulated value; means for generating a basic waveform based on the second accumulated value; It is provided with.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
[0012]
FIG. 1 shows a block configuration of an electronic musical instrument to which a modulation waveform generator of the present invention is applied. The electronic musical instrument includes a central processing unit (CPU) 101, a read only memory (ROM) 102, a random access memory (RAM) 103, a timer 104, a drive device 105, a MIDI interface 107, a network interface 108, a panel switch 109, and a panel display. 110, sound source 120, waveform memory 128, digital-to-analog converter (DAC) 130, and sound system 131.
[0013]
The CPU 101 is a processing device for controlling the operation of the entire electronic musical instrument. The ROM 102 is a nonvolatile memory that stores programs executed by the CPU 101 and various constant data. The RAM 103 is a volatile memory used for a load area for programs executed by the CPU 101 and various work memory areas. The timer 104 is a timer that supplies a clock signal having a predetermined period. The drive device 105 is a device that inserts a disk 106 as an external recording medium and reads / writes various data in accordance with instructions from the CPU 101. The MIDI interface 107 is an interface that is connected to an external MIDI device and exchanges signals according to the MIDI standard. The network interface 108 is an interface for connecting to an external network. A panel switch 109 indicates operators such as various switches provided on the external panel of the electronic musical instrument. The panel display 110 is a display provided on the panel of the electronic musical instrument.
[0014]
The sound source 120 includes a sound source control register 121, an LFO (modulation waveform generation unit) 122, an address generation unit 123, an interpolation unit 124, a DCF (frequency characteristic control unit) 125, an EG (envelope generator) 126, and a mixer & DSP 127. The sound source 120 operates in a time division manner for a plurality of channels. That is, a so-called 1DAC period (one sampling period) is divided by the number of channels, and a musical tone generation process is performed for each channel in each divided time section.
[0015]
The sound source control register 121 serves as an interface between the CPU 101 and the sound source 120. The CPU 101 writes various instruction commands to the sound source 120 by writing a predetermined value in a predetermined register in the sound source control register 121. The sound source control register 121 will be described in detail later. The address generator 123 generates an address for reading predetermined waveform data in the waveform memory 128 in accordance with an instruction from the CPU 101. The read waveform data is interpolated by the interpolation unit 124 and input to the DCF 125. The DCF 125 gives a timbre change to the input signal. The EG giving unit 126 gives an envelope to the input signal. After mixing the input signal and applying various effects, the mixer & DSP 127 outputs a musical sound signal to the DAC 130 as a final sound source output. The DAC 130 converts the input digital musical tone signal into an analog musical tone signal. The converted analog tone signal is emitted by the sound system 131.
[0016]
The LFO waveform generated by the LFO 122 is input to the address generator 123, the DCF 125, the EG adder 126, and the mixer & DSP 127. The LFO waveform input to the address generator 123 serves as a pitch modulation waveform for frequency modulating the address. The LFO waveform input to the DCF 125 serves as a timbre modulation waveform that changes the timbre. The LFO waveform input to the EG applying unit 126 plays a role of an amplitude modulation waveform when applying an envelope. The LFO waveform input to the mixer & DSP 127 is used for pan changes or various effect processing such as reverb or chorus.
[0017]
FIG. 2 shows an example of an LFO waveform generated in the LFO 122. The five-line notation and notes indicate the musical tone of the automatic performance. A waveform 201 below is an example of an LFO waveform generated in synchronization with the tempo of this automatic performance. For example, the pan pot (sound image position) is localized to the left at the start position of one measure (the stereo L volume level is maximum and the R volume level is 0), and the pan pot is gradually moved within the measure. When it is desired to perform panning by moving from the left side to the right side and panning the pan pot to the right side at the bar end position, this LFO waveform 201 is supplied to the panning circuit of the mixer & DSP 127. The LFO waveform 201 plays a role of a waveform that defines the position where the pan pot is localized, and is assumed to be localized to the left at the lowest level of the LFO waveform 20 and to the right at the highest level. When such panning is performed, if the tempo of automatic performance and the LFO waveform are not synchronized, desired panning cannot be performed at each measure. In this embodiment, since an LFO waveform synchronized with the tempo of automatic performance is generated, panning synchronized with the tempo of automatic performance can be performed at each measure.
[0018]
In order to generate the LFO waveform 201 synchronized with the tempo of the automatic performance, a tempo synchronization trigger based on the F8 signal that is a tempo clock is supplied from the CPU 101 side to the LFO 122. That is, the CPU 101 supplies a tempo synchronization trigger to the sound source 120 at the timing of the F8 signal as will be described later. When the LFO 122 receives a tempo synchronization trigger based on the F8 signal, the LFO 122 performs a process of correcting a synchronization deviation with respect to the tempo, such as changing to the next target value of the counter, and thereby an LFO waveform synchronized with the tempo of the F8 signal as much as possible. Process to output. This process will be described later.
[0019]
FIG. 3 shows a detailed configuration of the LFO 122 of FIG. The LFO 122 includes a trigger counter 301, a common counter 302, a low frequency oscillation unit 303 for each channel, and a low frequency oscillation unit 305 for DSP. One trigger counter 301 and one common counter 302 are provided in the LFO 122. Each channel low-frequency oscillator 303 is provided for each sound generation channel. Here, 128 low-frequency oscillators 303 for 128 channels are provided. A plurality of low frequency oscillators 305 for DSP are provided to generate a plurality of modulation waveforms used in the mixer & DSP 127. Here, DSP low frequency oscillators 305 for 64 channels are provided.
[0020]
Each sound channel low-frequency oscillation unit 303 includes an N-times processing unit 331, a reset control unit 332, an offset addition unit 333, a shape transformation unit 334, a linear interpolation unit 335, phase inversion units 336, 338, and 340, and a depth control unit 337. , 339, 341, and an asynchronous counter 342. Each DSP low-frequency oscillation unit 305 includes an N-times processing unit 351, a reset control unit 352, an offset addition unit 353, a shape transformation unit 354, a primary LPF 355, and an asynchronous counter 356.
[0021]
The trigger counter 301 and the common counter 302 are counters each composed of an integer part 17 bits and a decimal part 10 bits for generating a basic sawtooth wave (referred to as a base waveform) from which an LFO waveform to be output is generated. is there. A desired LFO waveform is obtained by processing the generated base waveform by the low-frequency oscillation unit 303 for each channel or the low-frequency oscillation unit 305 for the DSP.
[0022]
The trigger counter 301 is a counter that adds the trigger counter up value to the current value each time a tempo synchronization trigger is supplied from the CPU 101 and outputs the value after the addition as a new current value. The current value of the trigger counter 301 becomes the target value of the common counter 302. The tempo synchronization trigger is a trigger supplied from the CPU 101 to the sound source 120 at the timing of the F8 signal, and is a trigger action described later. The trigger counter up value is calculated and set by the CPU 101.
[0023]
The common counter 302 is a counter that accumulates a common counter interpolation rate for each sampling period. The CPU 101 calculates and sets the common counter interpolation rate. If the accumulated value of the common counter 302 reaches the value of the trigger counter 301 before the next tempo synchronization trigger comes, the accumulation for every sampling period of the common counter 302 is stopped there. When the next tempo synchronization trigger comes, if the accumulated value of the common counter 302 has not yet reached the value of the trigger counter 301, the accumulated value of the common counter 302 has been set as the target value until then. Force the value to. The output of the common counter 302 becomes a base waveform (sawtooth wave) 201 as shown in FIG.
[0024]
The base waveform (integer part 17 bits + decimal part 10 bits) from the common counter 302 is input to the N-times processor 331 of the low-frequency oscillator 303 of each channel. The N-times processing unit 331 multiplies the output waveform of the common counter 302 by N (however, the number of bits in the integer part is not increased). The fractional part of the multiplication result is rounded down to generate a sawtooth wave having a period of 1 / N of the period of the base waveform and consisting of only 17 bits of the integer part. The multiplier N is set by the CPU 101 independently for each tone generation channel.
[0025]
The output of the N-times processing unit 331 is input to the reset control unit 332. Note that the waveform data of each block after the reset control unit 332 is composed of only 17 bits of the integer part. When the key-on reset flag that instructs to set the LFO waveform to the initial phase at the same time as the key-on is set to “valid”, the reset control unit 332 outputs N times the current sound output channel when the note-on is performed. Is controlled to be “0”. Specifically, an N-fold output value when each sound channel is note-on is taken into a register, and the value of the register is subtracted from the subsequent N-fold output value (however, the number of bits in the integer portion is Do not increase). Thereby, the output of the reset control part 332 becomes a waveform forcibly starting from zero. If the key-on reset flag is set to “invalid”, the “loading of the N times output value to the register” is not performed. That is, the value fetched in the register at the time of note-on is not changed, and the process of subtracting the value of the register from the N-fold output value and outputting is continued.
[0026]
The output of the reset control unit 332 is input to the offset adding unit 333. The offset adding unit 333 adds an offset value set for each tone generation channel to the input waveform (however, the number of bits in the integer part is not increased). This offset value is the initial phase when the key-on reset flag is reset with “valid”. The CPU 101 sets this offset value. The reset control unit 332 and the offset addition unit 333 can generate an LFO waveform starting from an arbitrary initial phase.
[0027]
The output of the offset adding unit 333 is input to the shape deforming unit 334. The shape deforming unit 334 converts the input sawtooth wave into a waveform having various shapes such as a triangular wave, a rectangular wave, and a sine wave according to the shape selection information, and outputs the waveform. Here, the sawtooth wave serves as phase data for generating waveforms of various shapes. Therefore, in this conversion, only the shape is converted with the same period, or a sawtooth wave can be output as it is. The shape selection information is set by the CPU 101 for each sound generation channel.
[0028]
The output of the shape deforming unit 334 is input to the linear interpolation unit 335. The linear interpolation unit 335 performs control so that the slope (change) of the input waveform is equal to or less than the set waveform interpolation rate. The CPU 101 sets the waveform interpolation rate for each sound generation channel. The interpolation by the linear interpolation unit 335 is for smoothing a waveform for the purpose of noise removal.
[0029]
The output of the linear interpolation unit 335 is input to the phase inversion units 336, 338, and 340, respectively. The phase inversion units 336, 338, and 340 can select phase inversion (normal phase / reverse phase) for each output destination (address generation unit 123, DCF 125, EG adding unit 126) of each sound generation channel. For example, the pitch and amplitude can be modulated in the same phase or in opposite phases. In addition, the amplitude modulation of sounds generated by a plurality of sound generation channels can be in phase (through) or in reverse phase (all bit inversion). The CPU 101 sets whether to invert the phase.
[0030]
The outputs of the phase inversion units 336, 338, and 340 are input to the depth control units 337, 339, and 341, respectively. In the depth control units 337, 339, and 341, the modulation depth can be set for each output destination (address generation unit 123, DCF 125, EG adding unit 126) of each sound generation channel. The CPU 101 sets the modulation depth. The outputs of the depth control units 337, 339, and 341 are respectively input to the address generation unit 123 as a pitch modulation waveform, to the DCF 125 as a tone color modulation waveform, and to the EG provision unit 126 as an amplitude modulation waveform.
[0031]
The low frequency oscillating unit 303 of each sound generation channel can be operated as a tempo synchronization LFO or can be operated as a tempo asynchronous LFO according to the setting for each sound generation channel. The designation is performed by the CPU 101. The asynchronous counter 342 is a counter used to generate a modulation waveform having a frequency corresponding to set frequency data when operating as a tempo asynchronous LFO. In the LFO 303 set to operate as a tempo asynchronous LFO, the unit of the period of the generated LFO waveform is specified by a period time or a frequency. This cycle time or frequency is designated by the CPU 101. Asynchronous counter 342 generates a modulation waveform having a frequency corresponding to a specified cycle time or frequency.
[0032]
Note that when the low-frequency oscillation unit 303 of a certain tone generation channel is operated as a tempo asynchronous LFO, the N-times processing unit 331 and the reset control unit 332 for that channel are not necessary. Therefore, the register of the reset control unit 332 is also used as a register that holds the current value of the asynchronous counter 342. The register that holds the multiplier N of the N-times processing unit 331 is also used as a register that holds “cycle time or frequency” designated by the CPU 101.
[0033]
The internal configuration of each DSP low-frequency oscillator 305 is the same as the low-frequency oscillator 303 of each tone generation channel described above. The N-fold processing unit 351 is the N-fold processing unit 331, the reset control unit 352 is the reset control unit 332, the offset adding unit 353 is the offset adding unit 333, the shape deforming unit 354 is the shape deforming unit 334, and the asynchronous counter 356 is These correspond to the asynchronous counters 342, respectively. However, a linear LPF 355 for smoothing is provided instead of the portion after the linear interpolation unit 335. The amplitude level of the LFO waveform generated by the low-frequency oscillator 305 is controlled by a multiplier in an algorithm realized by a microprogram in the DSP. With this configuration, a plurality of LFO waveforms that are assigned to each effect process in the mixer & DSP 127 are generated.
[0034]
As described above, the DSP is provided with a plurality of EGs together with a plurality of LFOs assigned to each effect. The plurality of LFOs and the plurality of EGs are assigned to each effect in the number required for each effect executed by the DSP, so that each one can be individually triggered. Yes. For example, in the case of a chorus effect using three LFOs, the three LFOs need to be operated with phases shifted from each other by 120 degrees. This can be realized by setting initial phases different by 120 degrees in the offset adding unit 353 for the LFOs for 3 LFO channels and simultaneously resetting them. If a trigger is used, it is also possible to execute waveform generation processing (similar to the waveform generation unit) instead of the effect by the DSP.
[0035]
Next, registers and flags related to tempo synchronization LFO will be described. Since the trigger counter 301 and the common counter 302 have been described with reference to FIG. 3, the other registers and flags (sound source control register 121) will be described in the following (1) to (14).
[0036]
(1) Trigger counter up value register: This register holds a value to be added to the trigger counter 301 for each F8 signal (tempo synchronization trigger). The value written here determines how many triggers make one cycle. Here, the trigger counter 301 is a register that can count up to 2 to the 17th power −1 = 131071 with its integer part 17 bits, and about 2 to the 17th power to about 131072 with the decimal part included, so this maximum value is the base. The trigger counter up value is obtained by dividing by the number of F8 signals in one period of the waveform. The CPU 101 sends the calculated value to the sound source 120 and stores it in the trigger counter up value register. When the trigger counter up value is not divisible, the quotient is rounded up. By rounding up, the trigger counter 301 always overflows with the last F8 signal in one cycle of the base waveform. The overflow overflowed at this point is discarded, and the trigger counter 301 is initialized to zero. Therefore, an error when it cannot be divided is not accumulated.
[0037]
A calculation example of the trigger counter up value by the CPU 101 will be described. The CPU 101 determines the period of the base waveform according to the LFO waveform to be output. For example, assume that the tempo is 120 quarter-note tempo per minute, 96 F8 signals are generated in one bar, and the base waveform cycle is one bar (four quadrants). Think about the case. In this case, since the number of F8 signals in one measure is 96, a trigger counter up value to be added to the trigger counter 301 for each F8 signal can be calculated from here. That is, since the maximum value of the trigger counter 301 is 2 17 = 131072, it is set to 131072 / 96≈1365.3333, and this value is rounded up to obtain the trigger counter up value. For example, if the trigger counter up value is 4 bits for the exponent part and 12 bits for the mantissa part, the rounded up value is 1365.5. Actually, since the trigger counter 301 and the trigger counter up value register store values in a floating-point binary number, rounding up is also rounded up in binary number. Thus, the trigger counter up value is calculated by the equation of RU (maximum value / number of F8 signals) based on the number of F8 signals in one cycle of the base waveform. Here, RU () indicates rounding up.
[0038]
(2) Common counter interpolation rate register: The common counter 302 is an interpolator that linearly interpolates using the value of the trigger counter 301 as a target value for each DAC cycle. It is the common counter interpolation rate that specifies the interpolation speed for this interpolator. The common counter interpolation rate register is a register that holds the common counter interpolation rate. The common counter interpolation rate must be specified in consideration of the step width (number of divisions) determined by the trigger counter up value and how much time, that is, how much tempo is used for interpolation. is there.
[0039]
An example in which the CPU 101 calculates the common counter interpolation rate in the case of the trigger counter up value calculation example (1) above will be described. First, in the above case, one quarter note has a time length of 60 sec / 120≈0.5 sec. Since one quarter note is a time interval for 24 F8 signals, the time interval for one F8 signal (the time interval from the F8 signal to the next F8 signal) is 0.5 sec / 24≈0.0208 sec. . Since we want to set the period of the base waveform to one measure (time interval for 96 F8 signals), 0.0208 sec × 96≈2 sec is the period of the base waveform. Assuming that the sampling frequency in the sound source is 44100 Hz, the period is 22 μsec. Therefore, the accumulation to the common counter 302 is performed 2 sec / 22 μsec≈88200 times within one period of the base waveform. Since the maximum value of the common counter 302 is 2 17 = 131072, 131072 / 88200≈1.4861, and if the common counter interpolation rate is composed of 4 bits for the exponent part and 12 bits for the mantissa part, it is rounded up in binary. About 1.4863 is the value. In this way, the common counter rate is calculated by the formula of RU (maximum value / number of samples) based on the number of samples in one period of the base waveform.
[0040]
(3) Trigger action flag: The trigger action is a trigger (tempo synchronization trigger) that gives an event for tempo synchronization from the CPU 101. When 1 is written to the trigger action flag from the CPU 101, the tempo synchronization trigger is supplied to the LFO 122. By this trigger, the trigger counter up value is added to the trigger counter 301, and the value becomes a new target value, and interpolation by the common counter 302 starts toward the target value.
[0041]
(4) Trigger counter reset flag: This is a flag for resetting the trigger counter 301 added by the tempo synchronization trigger. Used for initialization such as tempo synchronization. When 1 is written, the reset state is entered at that timing, and it is not necessary to write 0.
[0042]
(5) Common counter reset flag: A flag for resetting the common counter 302 which is a linear interpolator. Used for initialization such as tempo synchronization. When 1 is written, the reset state is entered at that timing, and immediately thereafter, the common counter 302 starts counting up at the set common counter interpolation rate. There is no need to write 0.
[0043]
(6) Free-run mode flag: Normally, the common counter 302 operates with the value of the trigger counter 301 as a target value. When this free-run mode flag is set to 1, the common counter 302 ignores the target value. Always continue to interpolate at a given rate. As a result, even if there is no tempo synchronization event, the common counter 302 operates at almost the same speed as in tempo synchronization. On the other hand, when the common counter 302 performs a normal tempo synchronization operation, the free-run mode flag is set to zero. When the free run mode flag is set to 0, the interpolation processing by the common counter 302 is stopped, and the value at the time of the stop is continuously output.
[0044]
(7) Channel-by-channel tempo synchronization flag: Whether to operate at a channel-independent frequency setting for each low-frequency oscillation unit 303 (conventional type) or whether to operate in synchronization with the tempo-synchronized common counter 302 It is a flag to switch. Setting this flag to 1 synchronizes with the common counter 302 (that is, using the waveform generated by the flow of the N-times processing unit 331 → reset control unit 332 → offset adding unit 333 in FIG. 3), and setting it to 0 makes the channel Independent frequency setting LFO (that is, the waveform generated by the flow of the asynchronous counter 342 → offset adding unit 333 is used in FIG. 3).
[0045]
(8) N-by-channel setting register: A register for setting a multiplier N value of the N-times processing unit 331 for each channel when used as a tempo synchronization LFO. This register is shared with the frequency register for each channel when used as a tempo asynchronous LFO.
[0046]
(9) Key-on reset flag: A flag that determines whether or not to set the LFO waveform to the initial phase simultaneously with key-on (synonymous with note-on). When 0, it is “invalid”, that is, it is not reset by key-on. When it is 1, “valid”, that is, reset by key-on.
[0047]
(10) Offset value register: This register holds an offset value to be added to the LFO waveform by the offset adding unit 353.
[0048]
(11) Waveform selection register: a register that holds the shape selection information of the waveform shape converted and output by the shape deforming unit 334. The waveforms that can be selected will be described in detail later.
[0049]
(12) Waveform interpolation rate register: A register for holding an interpolation rate when the linear interpolation unit 335 performs interpolation.
[0050]
(13) Phase inversion designation register: A register that holds selection information for selecting phase inversion (normal phase / reverse phase) in the phase inversion units 336, 338, and 340.
[0051]
(14) Depth designation register: a register for setting the depth of modulation in the depth control units 337, 339, and 341.
[0052]
Of the above registers and flags, (1) to (6) are provided one by one in the system. (7) to (14) are provided for each channel (a channel is a sound generation channel in the low frequency oscillation unit 303 of each sound generation channel, and each LFO channel in each low frequency oscillation unit 305 for DSP). is there. However, each low frequency oscillation unit 305 for DSP does not have the registers (12) to (14).
[0053]
FIG. 4 shows how the trigger counter 301 and the common counter 302 count up. FIG. 4A shows a case where the F8 signal (tempo synchronization trigger) is supplied at regular intervals. Here, since the CPU 101 gives a trigger action to the LFO 122 of the sound source 120 in response to the generation of the F8 signal, the timing at which the F8 signal is generated is equivalent to the timing of the trigger action. Although it is recognized as the timing of the trigger action in the sound source 120, in FIG. 4, the timing is indicated by an F8 signal for simplification of explanation. Here, for the sake of simplicity of explanation, the number of occurrences of the F8 signal per period of the base waveform is set to four, but the number of occurrences of the normal F8 signal is considerably larger than this.
[0054]
A graph 401 that changes stepwise at the timing at which the F8 signal is supplied indicates the value of the trigger counter 301. The value of the trigger counter 301 becomes the trigger counter up value at the timing of the first F8 signal in one cycle of the base waveform, and thereafter, the trigger count up value is added to the value every time the F8 signal comes. The common counter 302 is finely interpolated using the value of the trigger counter 301 as a target value and counted up. Reference numeral 402 denotes the value of the common counter 302 that is ideally counted up toward the target value. If the accumulated value of the common counter 302 has not yet reached the target value of the trigger counter 301 at the timing of the next F8 signal, the accumulated value of the common counter 302 is set to the value of the trigger counter 301 that is the target value. Shows the graph forcibly set. 404, the accumulated value of the common counter 302 reaches the target value of the trigger counter 301 before reaching the timing of the next F8 signal, from which the accumulation of the common counter 302 is stopped and the target value is output. The graph which continues doing is shown.
[0055]
Reference numeral 410 denotes a level of 2 17 = 131072, which is the maximum value of the counter. The trigger counter 301 overflows at the timing of the last F8 signal (fourth in this figure) in one cycle of the base waveform, and in response to the overflow, the internal value of the trigger counter 301 is reset to 0, while the common counter In contrast, the maximum value (about 131072) is output. In the example of this figure, the calculation of the trigger counter up value is divisible (131072/4 = 32768), but even in that case, the addition result is 17 in the integer part by the addition according to the last F8 signal. Overflow occurs beyond the bit. After the value of the common counter 302 reaches the maximum value 131072, the maximum value is continuously output.
[0056]
FIG. 4B shows a case where the F8 signal is irregular. Since the tempo of automatic performance can be arbitrarily changed, the F8 signal may be generated irregularly. Even when the F8 signal is irregular, the count-up operation is the same, so the same numbers as in FIG. In FIG. 4B, the trigger counter 301 is reset to 0 at the timing of the F8 signal 411, from which the common counter 302 continues to accumulate the common counter interpolation rate, but the value of the common counter 302 is the maximum value. The next F8 signal 412 arrives before the counter reaches, and the common counter 302 is reset to zero.
[0057]
FIG. 5 shows various examples of count-up using the trigger counter 301 and the common counter 302. As described above, the CPU 101 determines the period of the base waveform, obtains the number of F8 signals within the period, calculates the amount added to the trigger counter 301 for each F8 signal, and calculates the common counter interpolation rate. In this case, it is necessary to send F8 signals from the CPU 101 side to the LFO 122 at equal intervals. FIG. 5A shows an example in which the F8 signal is sent at a timing obtained by finely dividing one period of the base waveform. A plurality of horizontal lines 501 indicate each level at which the trigger counter 301 is counted up stepwise. The F8 signal is supplied to the LFO 122 at equal intervals as indicated by 502, and the counter 301 is counted up stepwise at the timing of each F8 signal. Reference numeral 503 is a graph of the common counter 302. As described above, when the F8 signal is transmitted at a fine cycle, it is possible to precisely follow various tempo changes occurring in the middle of one cycle of the base waveform.
[0058]
FIG. 5B shows an example of thinning out the F8 signal. If it is known that the tempo does not fluctuate much during each period of the base waveform, the intermediate F8 signal can be thinned out in this way. The CPU 101 determines the period of the base waveform and determines how many F8 signals are to be included in the period. At this time, some F8 signals are thinned out from the original number of F8 signals. Based on the F8 signal remaining after the thinning, a trigger counter up value that is an addition amount for each F8 signal is calculated. In this case, since the F8 signal is generated only once per period of the base waveform, the trigger counter up value is set to a special maximum value that causes an overflow in the first addition. Further, only the F8 signal is thinned out from the example of FIG. 5A, and the slope of the base waveform is the same, so the common counter interpolation rate may be the same value as in FIG. In this example, the CPU 101 only needs to give a trigger action to the LFO 122 once every period of the base waveform, and the load on the CPU 101 is small.
[0059]
FIG. 5C shows an example in which the common counter interpolation rate is changed during one cycle of the base waveform. The CPU 101 determines the period of the base waveform and determines how many F8 signals are to be included in the period. Then, a trigger counter up value that is an addition amount for each F8 signal is calculated. In the example of this figure, the addition amount is obtained by dividing into three equal parts. On the other hand, the common counter interpolation rate is the quotient obtained by dividing twice the trigger counter up value by the number of samples from timings 521 to 522 in the first half of one cycle of the base waveform, and the trigger counter up value from timings 522 to 523 in the second half. Calculated as the quotient divided by the number of samples. As shown in the figure, the CPU 101 gives trigger actions at unequal intervals in each period of the base waveform. In addition, the CPU 101 gives the first half common counter interpolation rate at the timings 521 and 523 at the beginning of one cycle of the base waveform, and gives the second half common counter interpolation rate at the middle 522 timing.
[0060]
FIG. 5D is an example in which the F8 signal is thinned out instead of changing the trigger counter up value in the middle of one cycle of the base waveform in FIG. 5C. In this case as well, since the slope of the base waveform is the same as in FIG. 5C, the common counter interpolation rate may be the same as in FIG. On the other hand, the trigger counter up value is calculated with the first half of one period of the base waveform being 2/3 of the maximum value and the second half being 1/3. The CPU 101 gives the base counter up value in the first half at the timings 531 and 533 at the beginning of one cycle of the base waveform, and gives the base counter up value in the second half at the middle 522 timing. Further, the first half common counter interpolation rate is given at the timings 534 and 536 at the beginning of one cycle of the base waveform, and the second half common counter interpolation rate is given at the middle 535 timing. As described above, when generating a base waveform for changing the common counter interpolation rate in the middle of one cycle, the CPU 101 only controls the trigger action, the base counter up value, and the common counter interpolation rate for the timing of the change. Good.
[0061]
FIG. 6 shows a processing method when the F8 signal is interrupted. At the end of a song, the F8 signal that is a tempo counter may be interrupted. In this case, either of the processing methods shown in FIGS. 6A and 6B can be adopted according to the above-described free-run mode flag. FIG. 6A shows a case where the free-run mode flag is left as 0 even after the F8 signal is interrupted. In this case, as the value of the trigger counter 301 does not increase at the timing when the F8 signal stops, the value of the interpolation counter does not change from the same value. FIG. 6B shows a case where the free run mode flag is set to 1 when the CPU 101 detects that F8 has stopped. In this case, the common counter 302 always performs interpolation at a given common counter interpolation rate ignoring the target value. As a result, the LFO waveform can be continuously applied to a musical sound that is output after the music is finished.
[0062]
FIG. 7 shows an example of processing performed by the N-times processing units 331 and 351 described above. Reference numeral 701 denotes a base waveform input from the common counter 302 to the N-times processing units 331 and 351. If the multiplier N in the N-times processing units 331 and 351 is 9, the output of the N-times processing units 331 and 351 will be a waveform 702. The frequency of this waveform 703 is nine times the frequency of the base waveform 701.
[0063]
FIG. 8 shows a list of multipliers N of the N-times processing units 331 and 351 described above. “Quarter note reference number” in the top row of the table indicates how many quarter notes are included in one period of the base waveform. Since one quarter is made up of four quarter notes, the length of one cycle of the base waveform can be expressed by the number of bars as shown in “bar” in the lower row. Since one quarter note is 24 F8 signals, the number of F8 signals within one period of the base waveform in each case is obtained. The “F8 signal number” row indicates the value.
[0064]
The descriptions such as “4 minutes × 32 (8 bars)” and “4 minutes × 16 (4 bars)” on the left side indicate the period of the LFO waveform to be generated in each sound generation channel or each LFO channel. For example, if there are three “quarter note reference numbers”, one period of the base waveform is three quarter notes, and you want to generate a waveform with a period of “all three notes” for this base waveform. It can be seen that N = 1.125 may be set. Similarly, based on this list, the multiplier N can be obtained from the period of the base waveform and the period of the waveform to be generated. Note that even if it is not described in FIG. 8, the multiplier N can be obtained from the period of the base waveform having an arbitrary length and the period of the waveform to be generated having an arbitrary length.
[0065]
FIG. 9 shows examples of waveform shapes that can be selected for each channel by the shape deforming units 334 and 354. The shape deforming units 334 and 354 can generate and output a triangular wave 901, a rectangular wave 902, a sawtooth wave 903, a sine wave 904, a random wave 905, and the like based on the input base waveform. The waveforms listed here are merely examples, and other arbitrary waveforms may be selected.
[0066]
FIG. 10 shows an example of linear interpolation by the linear interpolation unit 335. The linear interpolation unit 335 performs interpolation for limiting the slope of the input waveform to be equal to or lower than a set interpolation rate. The CPU 101 determines the interpolation rate in accordance with the waveform shape selected in the sound generation channel or LFO channel of the LFO 122 and the set N times value, and supplies the linear interpolation unit 335 with the interpolation rate. For example, when the input waveform is a sawtooth waveform as indicated by 1001, a waveform such as the waveform 1002 is output when the interpolation rate value is decreased. By this interpolation, it is possible to prevent noise from occurring at a portion where the LFO waveform changes rapidly.
[0067]
Next, a processing procedure executed by the CPU 101 will be described with reference to a flowchart.
[0068]
FIG. 11 shows a flow of main processing executed by the CPU 101. In step 1101, initialization is performed, and in step 1102, the occurrence of an activation factor (event) is checked. If there is any activation factor in step 1103, the process proceeds to step 1104. If there is no activation factor, the process returns to step 1102 to continue the activation factor check. In step 1104, what factor is determined, and the process branches to one of steps 1105 to 1109 depending on the factor. If there is a panel operation event, the process proceeds to step 1105 to perform panel processing and then returns to step 1102. If there is a MIDI event, the process proceeds to step 1106, performs MIDI event processing, and then returns to step 1102. If there is a tempo interruption event, the process proceeds to step 1107 to perform automatic performance tempo interruption processing, and then returns to step 1102. If it is another event, the process proceeds to step 1108, performs processing according to the event, and then returns to step 1102. If the event is a power switch off event, an end process is performed in step 1109 and then the process ends.
[0069]
FIG. 12 shows the operation when the F8 signal from another MIDI device is received via the MIDI interface 107 in the MIDI event processing in step 1106. This is a case where the electronic musical instrument operates as a slave. That is, this electronic musical instrument performs an automatic performance based on automatic performance data output from another MIDI device, and the F8 signal as a tempo clock is supplied to the electronic musical instrument from the other MIDI device.
[0070]
In step 1201, the current tempo value is estimated based on the time interval of the past F8 signal and stored in the variable GT. In step 1202, a common counter interpolation rate is calculated based on the current tempo value GT and supplied to the LFO 122 of the sound source 120. The method for calculating the common counter interpolation rate has already been described. In step 1203, a tempo synchronization trigger is supplied to the LFO 122 of the sound source 120. This is done by writing 1 to the trigger action flag.
[0071]
FIG. 13 shows the operation when the note-on of automatic performance is received from the MIDI interface 107 in the MIDI event processing in step 1106. In step 1301, the received note-on part number is stored in the variable PT, the note number is stored in the variable NN, and the velocity is stored in the variable VEL. In step 1302, sound channel assignment processing is performed. In step 1303, various parameters are set in the channel assigned to the tone generator register 121 in accordance with the current tone color selected in the part PT, the note-on note number, and the velocity. That is, waveform selection information, F number, various EG parameters, LFO parameters, various send levels, etc. are set. Here, the LFO parameters include a tempo synchronization flag, a multiple N or frequency, an interpolation rate, a pitch modulation degree PMD, a tone color modulation degree CMD, an amplitude modulation degree AMD, and the like. When a timbre set to synchronize the tempo of the LFO waveform is selected in the part PT, a tempo synchronization flag is set. In step 1304, a note-on signal (sound generation start trigger) is supplied to the channel. In the sound generation channel to which the note-on signal is supplied, the tone signal forming process corresponding to the set parameter is started. That is, reading of waveform data from the waveform memory by the address generation unit 123 and the interpolation unit 124 is started, a timbre change is given to the read waveform data by the DCF 125, and further, the EG adding unit 126 stands up from the rising edge. Volume change until the drop is given. The LFO waveform generated by the LFO 122 is supplied to the address generating unit 123, the DCF 125, and the EG applying unit 126, and controls various characteristics of the tone waveform generated in the channel.
[0072]
FIG. 14 shows an operation when a variation type is received from the MIDI interface 107 in the MIDI event processing in step 1106. The variation type is information that specifies the type of effect to be added to the musical sound. In step 1401, the received variation type is stored in the variable VT. In step 1402, an MP (microprogram) number, an MP storage area, an LFO, and an EG are allocated. The DSP 127 includes a plurality of microprogram storage areas. By assigning MP numbers to these areas and setting and executing the microprograms, any effect processing can be executed in combination. The assignment of the MP number and MP storage area in step 1402 is to assign a number to the area where the effect microprogram specified by the variation type is loaded. In the LFO allocation, the required number of LFOs for a specified effect is allocated from the low-frequency oscillation units corresponding to a plurality of LFO channels indicated by reference numeral 305 in FIG. In addition, the EG (envelope generator) is allocated from among a plurality of EGs provided in the DSP 127, as many EGs as are necessary for the designated effect.
[0073]
Next, in step 1403, the assigned MP number effect is muted. In this case, when the effect processing of the MP number is being executed, muting is performed so that noise is not generated by switching micro programs. In step 1404, a tempo synchronization flag, a multiple N (frequency when used in asynchronous tempo), an LPF coefficient, a key-on reset flag, etc. are set for the assigned LFO channel. In step 1406, EG is set, and in step 1407, various coefficients are set. In step 1408, other necessary processing (delay memory processing, etc.) is performed. In step 1409, the mute applied in step 1403 is canceled, a trigger is given to start execution of the microprogram, and the process ends.
[0074]
FIG. 15A shows the procedure of the automatic performance tempo interruption process in step 1107 of FIG. During automatic performance, a timer interrupt is generated at a period corresponding to the current tempo, and this tempo interrupt process is executed at that time. This is a case where the electronic musical instrument operates as a master. That is, this electronic musical instrument reads automatic performance data and performs an automatic performance. The F8 signal is generated by this electronic musical instrument and supplied to another MIDI device. The time interval of tempo interruption may be set so that 24 interruptions per quarter note, which is the same as the F8 signal, or, for example, 96 interruptions per quarter note with a finer resolution. You may set as follows.
[0075]
First, at step 1501, the tempo counter is counted up. The tempo counter is a counter that defines the tempo of automatic performance on the CPU 101 side. Next, in step 1502, a tempo synchronization trigger is supplied to the LFO 122 of the sound source 120. In step 1503, the F8 signal is output to the MIDI output terminal. If the tempo interruption occurs at a finer resolution than the F8 signal, the tempo synchronization trigger may be supplied once in several times in step 1502, and the F8 signal is output once in several times in step 1503. do it. For example, if it is set so that 96 interrupts per quarter note are generated, the F8 signal is output once every 4 interrupts. In step 1504, it is determined whether the event timing of the automatic performance data has been reached. When the event timing is reached, the event is reproduced in step 1505, the duration up to the next event is set in step 1506, and the process ends. If it is not the event timing in step 1504, the processing is terminated as it is.
[0076]
In the event reproduction process in step 1505, for example, if a note-on event, the note-on process is performed. In step 1505, note-on reproduction may be performed. In step 1505, note-on is simply accumulated in the buffer, and note-on may be taken out from the buffer and processed in another processing routine.
[0077]
If the event in step 1505 is a tempo change, the process of FIG. 15B is performed. First, in step 1521, the designated tempo value is stored in the variable TMP. In step 1522, the speed of the tempo timer is changed according to the tempo value TMP. Next, in step 1523, a common counter interpolation rate corresponding to the tempo value TMP is supplied to the LFO 122 of the sound source 120, and the process is terminated.
[0078]
In the above embodiment, the tempo clock is not necessarily a MIDI “F8 signal” (resolution is 1/24 of one beat). The resolution may be, for example, 1/2 of a beat, 1/96, or the like. The value of the common counter interpolation rate to be added to the common counter 302 may be automatically determined based on the time interval immediately before the tempo clock. In the above embodiment, the common counter performs the interpolation operation (accumulation) for each sampling period. However, it may not be performed for each sampling period. For example, the interpolation calculation may be performed once every two sampling periods or once every eight sampling periods. Further, the tempo estimation based on the reception interval of the “F8 signal” may not be performed by the CPU 101 but may be performed by an arithmetic circuit in the sound source 120 to calculate the common counter interpolation rate in the sound source 120. The tempo may be estimated from only the time interval of the two “F8 signals” received immediately before (linearly), or from the multiple time intervals of the three or more “F8 signals” immediately before, by Lagrange interpolation. Etc. (curve) may be used.
[0079]
Note that the F8 signal may be generated by the CPU 101 using the timer 104, or may be generated externally and input from the MIDI interface 107 or the network interface 108.
[0080]
In the present embodiment, the F8 signal is used as a tempo signal, but any type of timing signal that controls other rhythms may be used as a tempo signal for synchronization.
[0081]
In this embodiment, the F8 signal indicating the tempo is used to synchronize with the automatic performance or the automatic accompaniment. However, it is not necessary to limit the present invention to such an F8 signal. This signal may be any signal indicating the timing for performing correction so that the tempo of the automatic performance or automatic accompaniment is synchronized with the bass waveform, and may be a tempo signal of a type other than the F8 signal. It may be a synchronous control signal generated periodically or irregularly in synchronization.
[0082]
The reset control unit 332 is reset to 0 in response to note-on, but may be reset to a predetermined value other than 0.
[0083]
In this embodiment, the base waveform is composed of an integer part of 17 bits and a decimal part of 10 bits, but is not limited to this number of bits, and may be increased or decreased as necessary.
[0084]
Although FIG. 6 shows the case where the F8 signal is interrupted with the end of the automatic performance, there may be a case where the F8 signal is missed due to an error. In that case, the CPU 101 may generate a dummy F8 signal so that the LFO waveform is not interrupted.
[0085]
【The invention's effect】
As described above, according to the present invention, a basic waveform having a predetermined bit width that circulates in a plurality of beats synchronized with the tempo is generated, the multiplier for each channel of a plurality of channels is multiplied by the basic waveform, and the multiplication result is obtained. When a value in which overflow has occurred with the predetermined bit width is output and a modulation waveform for each channel is generated based on the result, the LFO and the automatic performance means are provided independently. However, it can generate a modulated waveform that is synchronized with the tempo of automatic performance.
[Brief description of the drawings]
FIG. 1 is a block diagram of an electronic musical instrument to which a modulation waveform generating apparatus according to the present invention is applied.
FIG. 2 is a diagram showing an example of an LFO waveform generated in an LFO
FIG. 3 is a diagram showing a detailed configuration of an LFO
FIG. 4 is a diagram showing a state of count-up by a trigger counter and a common counter
FIG. 5 is a diagram showing various examples of count-up using a trigger counter and a common counter.
FIG. 6 is a diagram showing a processing method when an F8 signal is interrupted.
FIG. 7 is a diagram illustrating an example of processing performed by an N-times processing unit;
FIG. 8 is a diagram showing a list of multipliers N of an N-times processing unit
FIG. 9 is a diagram illustrating examples of waveform shapes that can be selected by the shape deforming unit;
FIG. 10 is a diagram illustrating an example of linear interpolation by a linear interpolation unit;
FIG. 11 is a flowchart of main processing.
FIG. 12 is a flowchart when an F8 signal is received from the MIDI interface 107;
FIG. 13 is a flowchart when an automatic performance note-on is received from the MIDI interface 107;
FIG. 14 is a flowchart when a variation type is received from the MIDI interface 107;
FIG. 15 is a flowchart of tempo interruption processing for automatic performance.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 101 ... Central processing unit (CPU), 102 ... Read-only memory (ROM), 103 ... Random access memory (RAM), 104 ... Timer, 105 ... Drive apparatus, 107 ... MIDI interface, 108 ... Network interface, 109 ... Panel switch 110 ... Panel display, 120 sound source, 128 ... Waveform memory, 130 ... Digital-to-analog converter (DAC), 131 ... Sound system.

Claims (3)

A modulation waveform generator for generating a plurality of modulation waveforms for use in a sound source having a plurality of channels for generating musical sounds,
Basic waveform generating means for generating a basic waveform of a predetermined number of bits that makes a round with a plurality of beats synchronized with the tempo;
Storage means for storing a multiplier for each channel of the plurality of channels;
Multiplication means for multiplying the basic waveform by a multiplier for each channel, and outputting a multiplication result waveform for each channel as a multiplication result waveform for each channel, among the multiplication results , the portion having the same number of bits as the basic waveform .
A modulation waveform generating device, comprising: modulation waveform generation means for generating a modulation waveform for each channel based on a multiplication result waveform for each channel output from the multiplication means . A modulation waveform generator for generating a plurality of modulation waveforms for use in a sound source having a plurality of channels for generating musical sounds,
Basic waveform generating means for generating a basic waveform of a predetermined number of bits that makes a round with a plurality of beats synchronized with the tempo;
Storage means for storing a multiplier for each channel of the plurality of channels;
Multiplication means for multiplying the basic waveform by a multiplier for each channel and outputting a predetermined number of bits of the multiplication result as a multiplication result waveform for each channel ;
A modulation waveform generating device, comprising: modulation waveform generation means for generating a modulation waveform for each channel based on a multiplication result waveform for each channel output from the multiplication means . The modulation waveform generator according to claim 1 or 2,
The basic waveform generating means includes
First accumulation means for accumulating a first predetermined value every time a tempo signal generated in synchronization with the tempo is received;
Second accumulating means for accumulating a second predetermined value at a predetermined cycle shorter than the cycle of the tempo signal and outputting a second accumulated value;
Coincidence control means for substantially matching the second accumulated value accumulated by the second accumulation means with the first accumulated value when the tempo signal is received;
A modulation waveform generator comprising: means for generating a basic waveform based on the second accumulated value .

Images