JPS6315914Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a musical sound waveform generator used in an electronic musical instrument.

Musical waveform generators used in electronic musical instruments include:
There are various configurations, but a typical one is to input the sound source waveform output from the sound source circuit to multiple waveform conversion circuits or filter circuits to change the sound source waveform, thereby creating the desired sound source waveform. There is one that produces a musical sound waveform. However, this device has the disadvantage that it becomes large in scale because it requires a waveform conversion circuit and a filter circuit for each tone, and it is difficult to obtain a tone that changes over time like a natural musical instrument. In this case, it was necessary to construct the above-mentioned filter circuit with a voltage controlled filter (VCF) or the like. However, since VCF is generally complex and expensive, it was not a good idea to configure it using VCF.

Recently, musical tone generation devices using digital technology (e.g., those using waveform memory reading methods, frequency modulation methods, harmonic synthesis methods, etc.) have been proposed, but these devices also generate multiple types of tones. However, if an attempt is made to generate a timbre that changes over time, the scale will increase and the price will inevitably increase.

This invention was made in view of the above-mentioned drawbacks of the conventional devices, and it is an object of the present invention to provide a musical sound waveform generating device that is small in scale and inexpensive, capable of generating musical sound waveforms of various tones.

According to this invention, there is provided a signal generating means for generating a plurality of signals, at least one of which is a periodic signal corresponding to the frequency of a musical sound waveform to be generated; waveform changing means for changing the waveform of the periodic signal by replacing the desired section with another signal,
A musical sound waveform is obtained from the output of the waveform changing means. In this case, musical sound waveforms of various tones can be obtained by appropriately selecting the contents of the plurality of signals generated by the signal generating means and the desired section in the waveform changing means.

Hereinafter, this invention will be described in detail with reference to an embodiment shown in the accompanying drawings.

FIG. 1 shows the basic configuration of a musical sound waveform generator according to this invention. In FIG. 1, an address generation circuit 1 repeatedly generates a predetermined address signal AD at a speed corresponding to the frequency of the musical tone to be generated, which is determined by pressing keys on a keyboard (not shown). An example of this address signal AD is shown in FIG. 2a. In FIG. 2a, the vertical axis shows the value of the address signal AD, the horizontal axis shows time,
The time T corresponds to the period of the musical tone to be generated.
Further, this address signal AD is given as digital data of multiple bits. Therefore, the second
The waveform shown in Figure a is originally a staircase wave, but is shown as a straight line for convenience of illustration.

The address discrimination circuit 2 receives the address signal AD generated from the address generation circuit 1, discriminates the value of the address signal AD, and generates a predetermined switching signal SS. That is, in this case, the address discrimination circuit 2 becomes "1" when the value of the address signal AD is within a predetermined range, and becomes "0" otherwise. For example, a switching signal SS as shown in FIG. 2b is generated. This switching signal SS becomes a selection signal in a selection circuit 4, which will be described later.

Similarly, the waveform generation circuit 3 is similar to the address generation circuit 1.
It receives the address signal AD generated from the address signal AD and repeatedly generates a musical sound waveform corresponding to the frequency of the musical tone to be generated. This waveform generation circuit 3 stores one period (or half a period) of a musical sound waveform as a plurality of amplitude sample values in each address, and sequentially designates each address in response to the address signal AD. A well-known waveform memory that repeatedly generates waveforms for periods can be used. FIG. 2c shows an example of the output waveform of this waveform generating circuit 3.

The selection circuit 4 has its A input supplied with the output of the waveform generation circuit 3 described above, and its B input supplied with a signal V ₀ at a constant level. Also selection control terminal
A switching signal SS output from the address discrimination circuit 2 is applied to SE. When the signal applied to the selection control terminal SE is "0", this selection circuit 4
Selects the signal to be applied to the input, and if it is "1", selects the signal to be applied to the B input. Therefore, when the switching signal SS is "0", the selection circuit 4 outputs the output of the waveform generation circuit 3, and when it is "1", the waveform becomes a constant level signal _V0 , as shown in FIG. 2d. Output. This waveform uses the determination content of the address discrimination circuit 2 and the signal V ₀ of a certain level as parameters, and by simply changing the determination content of the address discrimination circuit 2 or the level of the signal V ₀ , various musical tones corresponding to this change mode can be generated. Waveforms can be obtained.

FIG. 3 shows an embodiment of this invention. In this embodiment, two waveforms are generated: a waveform S directly output from the waveform generating circuit 3, and a waveform C formed by appropriately switching the output of the waveform generating circuit 3 with a signal V of a constant level. . Further, an envelope control circuit 5 is connected to the waveform generating circuit 3, and is adapted to give a predetermined amplitude envelope corresponding to a key press to the waveform generated from the waveform generating circuit 3. In the following drawings, the same reference numerals as those used in FIG. 1 are used for convenience of explanation for parts that perform the same functions as the circuit shown in FIG. 1, although they are originally separate parts.

In FIG. 3, the address generation circuit 1 repeatedly generates a predetermined address signal AD at a speed corresponding to the frequency of the musical tone to be generated. Waveform generation circuit 3
consists of a waveform memory that stores a half cycle of a sine wave in a resistive voltage divider circuit 31, decodes the address signal AD output from the address generation circuit 1 with a decoder 32, and sends this decoded signal through an OR circuit group 33. In addition to the gate group 34, the stored waveform is repeatedly read out. In other words, the potential at each voltage dividing point of the resistive voltage dividing circuit 31 is determined by each sample of the waveform (waveform in the interval represented by τ) from phase "π/2" to "3/2π" of the sine waveform shown in FIG. 4a. A signal from the OR circuit group 33 based on the output of the decoder 32 causes the resistor voltage divider circuit 31 to be first selected among the gates in the gate group 34.
Turn on the gate corresponding to the midpoint (point of phase π), then turn on the gates sequentially toward the point of phase π/2, and when the gate at the point of phase π/2 is reached, switch direction and phase The gates are turned on sequentially toward the point of 3/2π, and when the gate at the point of phase 3/2π is reached, the gates are again turned on sequentially toward the point of phase π, returning to the gate that was turned on first. As a result, a sine waveform for one period as shown in FIG. 4a is read out on the line 35. Here, the output of the envelope control circuit 5 is -V, and in FIG. 4, the vertical axis represents the level, the horizontal axis represents the address, and G represents the ground level. This waveform generation circuit 3
The waveform output from the waveform corresponds to the frequency of the musical tone to be generated, and this waveform is output as a waveform S.

Further, the address signal AD output from the address generation circuit 1 is applied to the address discrimination circuit 2.
The address discrimination circuit 2 includes decoders 21 and 2 that decode two different addresses A and B, respectively.
2 and the output of the decoder 21,
It consists of an RS flip-flop 23 that is reset by the output of the decoder 22. Now, if addresses A and B have values as shown in FIG. 4a, the output of the RS flip-flop 23 will be as shown in FIG. 4b.
The output signal of the flip-flop 23 is applied to the selection circuit 4 as the switching signal SS. The selection circuit 4 is composed of two gates 41 and 42. A signal obtained by inverting the switching signal SS by an inverter 43 is applied to the gate 41, and the switching signal SS is directly applied to the gate 42. Therefore, when the switching signal SS is "0", the gate 41 is turned on, the output of the waveform generation circuit 3 is selected, and the output becomes "1".
At this time, the gate 42 is turned on, and the signal -V at a certain level is selected and outputted from the selection circuit 4. The output waveform C of this selection circuit 4 is as shown in FIG. 4c. Constant level -V in this waveform C
The period of is determined by the decode address in the decoders 21 and 22, and the period of
By changing the configuration of 22, various waveforms corresponding to this variation can be obtained.

The envelope control circuit 5 is for providing the waveforms S and C with amplitude envelopes corresponding to key presses. In other words, the key-on signal KON becomes "1" only when the key is pressed (see Figure 5a).
When is "0", the gate 51 is off and the output of the envelope control circuit 5 is held at the ground level G. Therefore, even if address generation circuit 1 is operating, no output waveform is generated from waveform generation circuit 3. When the key-on signal KON becomes "1" due to key depression, the gate 51 is turned on, and the capacitor 53 is charged with a time constant determined by the resistance value of the resistor 52 and the capacitance value of the capacitor 53, and the envelope control circuit 5 is charged. The output gradually falls to the level -V as shown in FIG. 5b. After that, when the key is released and the key-on signal KON becomes “0”,
The gate 51 is turned off, and the charge in the capacitor 53 is discharged via the variable resistor 54. The time constant of this discharge is determined by the resistance value of the variable resistor 54 and the capacitance value of the capacitor 53. Therefore, when the key is released, the output of the envelope control circuit 5 changes as shown in FIG. 5b using the resistance value VR of the variable resistor 54 as a parameter. The output of this envelope control circuit 5 is applied to a resistive voltage divider circuit 31 of the waveform generation circuit 3. As a result, the output waveform S of the waveform generating circuit 3 is given an amplitude envelope as shown in FIG. 5b, and the waveform C is also given a similar amplitude envelope. The waveforms S and C, to which amplitude envelopes corresponding to the key presses are respectively applied, are appropriately mixed (mixing circuit not shown) and sent out as musical sound waveforms.

FIG. 6 shows another embodiment of this invention. This embodiment is configured so that a temporally changing waveform can be obtained by temporally changing the discrimination conditions of the address discriminating circuit 2.
This embodiment is the same as that shown in FIG. 3, except that the structure of the address discrimination circuit 2 is different from that shown in FIG. Therefore, the address discriminating circuit 2 will be mainly explained using the same reference numerals as in FIG.

In FIG. 6, the address discrimination circuit 2 includes a low frequency oscillator (LFO) 24 and a counter 25 for counting output pulses of the LFO 24. Here, the oscillation speed of the LFO 24 is sufficiently slower than the change speed of the address signal AD generated from the address generation circuit 1. The counter 25 first receives a key-on pulse that becomes "1" at the start of key depression.
It is reset to the initial value by KONP, and from then on
Each time a pulse is generated from the LFO 24, the count increases by one. The output of this counter 25 is applied to a comparison circuit 26. The comparison circuit 26 has the address signal AD generated from the address generation circuit 1 added to its other input, compares the output of the counter 25 with this address signal AD, and generates a match output EQ when the two match. . This matched output EQ is
It is applied to the set terminal S of the RS flip-flop 27. In addition, the address discrimination circuit 2 uses an address signal
A decoder 28 is provided which outputs a signal "1" when the value of AD reaches a predetermined address X, and the output of this decoder 28 is applied to the reset terminal R of the RS flip-flop 27. Here, address X related to decoder 28 is always counter 2
It is set to always be larger than the calculated value K of 5 (X≧K). That is, when the count value K reaches X, the counter 25 outputs a signal via the line 25a, and this signal causes the counter 25 to stop counting.

According to such a configuration, the address discrimination circuit 2
The RS flip-flop 27 is set by the coincidence output EQ of the comparison circuit 26, and
The reset timing is gradually delayed over time in accordance with the count value of the counter 25, and the output of the RS flip-flop 27 (switching signal SS) becomes as shown in FIG. 7a. . The selection circuit 4 selects the output of the waveform generation circuit 3 or the signal -V at a constant level by this switching signal SS.
Select. As a result, the selection circuit 4 obtains a waveform C as shown in FIG. 7b whose shape changes over time. In this case, the rate of change of the waveform shape is
It can be changed by changing the oscillation speed of the LFO 24, and the insertion point of the constant level signal -V can be changed by changing the decoded value of the decoder 28 and the maximum count value of the counter 25. can.

FIG. 8 shows still another embodiment of this invention. In this embodiment, two waveforms S16', C16', S8', C8', S4', C
4' is generated. In Figure 8,
The resistor voltage divider circuit 310 includes 31 voltage divider resistors R1 to R.
31, and these voltage dividing resistors R1 to R31
A predetermined waveform, in this case a half-cycle sine waveform, is stored at 32 voltage division points P ₀ to P ₃₁ by 32 sample points. Each of these partial pressure points P ₀ ~ _{P 31}
The output is 16 feet gate group 341, 8 feet gate group 342, 4 feet gate group 34
3 through lines 351, 352, 35 respectively
3.

In addition, in this embodiment, the address signal AD
is given as a 7-bit address code, all bits (7 bits) of this address signal AD are applied to the 16-foot decoder 321, and the lower 6 bits excluding the most significant bit MSB are 8 bits.
The signals of the lower 5 bits excluding the upper 2 bits of the most significant bit MSB and the second upper bit MSB are applied to the 4 foot decoder 323. The 16-foot decoder 321 receives the added 7-bit address signal.
AD is decoded into one line for two address values, and this is passed through OR circuit group 331 to 16
It is sequentially added to each gate in the foot gate group 341. To explain in more detail, when the address value of the address signal AD is 0 or 1, a signal “1” is output from the top line of the 16-foot decoder 321, and this signal “1” is outputted via the OR circuit group 331. First, the gate corresponding to the voltage dividing point P ₁₅ of the gate group 341 is turned on, and then, when the address value is 2 or 3, the second gate of the 16-foot decoder 321 is turned on.
A signal "1" is output from the upper line, and this signal passes through the OR circuit group 331 and turns on the gate corresponding to the voltage dividing point P ₁₆ immediately below the voltage dividing point P ₁₅ of the gate group 341, and the same goes on. Each gate of the gate group 341 is turned on in sequence downward, and when the gate corresponding to the voltage dividing point P ₃₁ is reached, each gate is turned on sequentially upward, and when the gate corresponding to the voltage dividing point P ₀ is reached. The gates are turned on one after another in a downward direction, and the process returns to the gate corresponding to the voltage dividing point _P15 . The above operation is then repeated. As a result, a musical tone signal having a sinusoidal waveform corresponding to twice the cycle of the address signal AD is read out on the line 351. Note that the envelope control circuit 5 is for applying a predetermined amplitude envelope to the sine waveform read out from the resistive voltage divider circuit 310, similar to the one shown in FIG. Further, the 8-foot decoder 322 decodes the lower 6 bits of the applied address signal AD, and sends it to the signals X0 to X0 through the OR circuit group 332.
X31 is sequentially added to each gate of the 8-foot gate group 342. In other words, first the address signal
If the value of the lower 6 bits of AD is 0, the signal
5 is generated, and this signal X15 turns on the gate corresponding to the voltage dividing point _P15 of the 8-foot gate group 342, and then the value of the lower 6 bits of the address signal changes to 1, 2, 3. ..., each gate of the 8-foot gate group is sequentially turned on downward by the output of the 8-foot decoder 322,
When the gate corresponding to the voltage division point P ₃₁ is reached, each gate is turned on in sequence in the upward direction, and when the gate corresponding to the voltage division point P ₀ is reached, each gate is turned on in sequence in the downward direction again. The process returns to the gate corresponding to pressure point _P15 , and this operation is repeated thereafter. As a result, a musical tone signal having a sinusoidal waveform having the same period as the address signal AD is read out onto the line 352. Similarly, the 4-foot decoder 323 uses the address signal
The signal of the lower 5 bits of AD is decoded, and this decoded signal is passed through the OR circuit group 333 to the signal Y0.
~Y31, in addition to the 4-foot gate group 343, turn on each gate in sequence. In this case, a musical tone signal having a sine waveform having a period of 1/2 of the address signal AD is read out on the line 353. The musical tone signals of sine waveform corresponding to periods twice, once, and half times the period of the address signal AD read out to the lines 351, 352, and 353 in this way have a waveform S16' representing a 16-foot tone. , a waveform S8' representing an 8-foot sound, and a waveform S4' representing a 4-foot sound. In addition, the above waveforms S16', S8', S4'
are added to the 16-foot selection circuit 401, the 8-foot selection circuit 402, and the 4-foot selection circuit 403, respectively. Selection circuit 40 for 16 feet
The selection circuit 402 for 1 and 8 feet and the selection circuit 403 for 4 feet are connected to the address discrimination circuit 201 for 16 feet and the address discrimination circuit 20 for 8 feet.
The switching signals SS16', SS8', and SS4' output from the 2- and 4-foot address discrimination circuits 203 are received, respectively, and these switching signals SS16', SS8',
Corresponding to SS4', the above waveforms S16', S8', S
By appropriately switching and selecting either the signal 4' or the constant level signal -V, the waveform S
Waveform C16', C different from 16', S8', S4'
8', C4' is formed. Here, the selection circuit 401 for 16 feet, the selection circuit 402 for 8 feet, and the selection circuit 403 for 4 feet have the same configuration as the selection circuit 4 shown in FIG. 3 or FIG. 6, and the address discrimination circuit for 16 feet. 201, 8-foot address discrimination circuit 202, and 4-foot address discrimination circuit 203 have the same configuration as the address discrimination circuit 2 shown in FIG. 3 or the address discrimination circuit 2 shown in FIG. However, the 16-foot tone is formed using all bits of the address signal AD, the 8-foot tone is formed using the lower 6 bits of the address signal AD, and the 4-foot tone is formed using the lower 5 bits of the address signal AD. Above, the address discrimination circuit 201 for 16 feet receives all bits (7 bits) of the address signal AD as input, and the address discrimination circuit 202 for 8 feet receives the signals of the lower 6 bits of the address signal AD except for the most significant bit MSB. The 4-foot address discrimination circuit 203 receives as input the signal of the lower 5 bits excluding the upper 2 bits MSB and MSB of the address signal AD.

In such a configuration, from the 16-foot selection circuit 401, the 8-foot selection circuit 402, and the 4-foot selection circuit 403, the
Musical tone signals representing a 16-foot tone, an 8-foot tone, and a 4-foot tone corresponding to the waveform shown in FIG. b are output.

FIG. 9 shows yet another embodiment of this invention. In this embodiment, the waveform A is formed by appropriately switching and selecting the output of the waveform generation circuit 3 and the signal V1 of a constant level in the selection circuit 4a based on the output of the address discrimination circuit 2a, and the output of the waveform generation circuit 3 and a constant level signal V2 are appropriately switched and selected by the selection circuit 4b based on the output of the address discrimination circuit 2b to form the waveform B, and by appropriately combining these two waveforms A and B via the resistor 6. This is the output waveform. In this case, the third address discrimination circuit 2a, 2b is
A structure similar to that of the address discriminating circuit 2 shown in the figure or FIG. 6 can be used.

Although the embodiment shown in FIG. 9 shows a case in which two systems of musical sound waveform generators are provided, it is also possible to provide a plurality of musical sound waveform generators of three or more systems and synthesize the formed waveforms as appropriate. You can also do this.

Further, in the embodiments described above, the waveform generation circuits have all been explained based on a waveform memory readout method using a resistive voltage divider circuit, but the present invention is not limited to this. For example, a similar configuration can be achieved using an FM waveform generation circuit.
The key point of this invention is to generate a signal with a waveform different from the periodic signal by appropriately switching between the output of a waveform generation circuit that generates a periodic signal corresponding to the frequency of the musical tone to be generated and a signal at a constant level. There is one implementation of. Here, the waveform generator may use any waveform generation method.

In addition, this idea is based on the output of one waveform generation circuit and the output of one waveform generation circuit.
The present invention is not limited to a configuration in which the two constant level signals are appropriately switched and selected. A configuration in which the outputs of a plurality of waveform generation circuits are appropriately switched and selected, a configuration in which the outputs of a plurality of waveform generation circuits and one constant level signal are appropriately switched and selected, and a configuration in which the outputs of one waveform generation circuit and a plurality of constant level signals are This invention also includes a configuration in which the signals are appropriately switched and selected, and a configuration in which the outputs of a plurality of waveform generation circuits and a plurality of constant level signals are appropriately switched and selected. Further, the constant level signal may change over time. Further, the mode of the above switching selection may be any mode as long as it maintains a predetermined periodicity in the output waveform. That is, a plurality of waveform generation circuits, at least one of which generates a periodic signal corresponding to the frequency of a musical tone to be generated, are provided, and one of the outputs of the plurality of waveform generation circuits, which includes the periodic signal, is used as the periodic signal. This idea is realized by appropriately switching and selecting within the cycle and using this as the output waveform.

As explained above, according to this invention, various waveforms can be obtained with a very simple configuration, and waveforms that change over time can also be easily obtained.
Musical tones with a wide variety of tones can be obtained using inexpensive equipment.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of this invention, FIG. 2 is a waveform diagram explaining the operation of the device shown in FIG. 1, and FIG. 3 is a circuit diagram showing an embodiment of this invention. 4 and 5 are waveform diagrams illustrating the operation of the embodiment shown in FIG. 3, FIG. 6 is a circuit diagram showing another embodiment of this invention, and FIG. 7 is a diagram showing the implementation shown in FIG. A waveform diagram explaining the operation of the example, and FIGS. 8 and 9 are block diagrams showing still other embodiments of this invention. DESCRIPTION OF SYMBOLS 1... Address generation circuit, 2... Address discrimination circuit, 3... Waveform generation circuit, 4... Selection circuit, 5
...Envelope control circuit.

Claims (1)

[Claims for Utility Model Registration] (1) Signal generating means for generating a plurality of signals, at least one of which is a periodic signal corresponding to the frequency of a musical sound waveform to be generated; No. 1
a waveform changing means for changing the waveform of the periodic signal by replacing a desired section in the period with another signal, and generating an output of the waveform changing means as a musical sound waveform. (2) The musical sound waveform generator according to claim (1), which changes the desired section over time. (3) The signal generating means includes a first circuit that generates a periodic signal corresponding to the frequency of the musical waveform to be generated, and a second circuit that generates a signal different from the periodic signal, and The changing means comprises a switching circuit that switches and outputs the output signal of the first circuit and the output signal of the second circuit at an appropriate timing within the period of the output signal of the first circuit. A musical sound waveform generator according to claim (1). (4) The first circuit includes an address generation circuit that generates an address signal that quickly and repeatedly changes in accordance with the frequency of a musical sound waveform to be generated, and a waveform that repeatedly generates a predetermined waveform in response to the address signal. A musical sound waveform generator according to claim (3) of the utility model registration claim, comprising a generating circuit. (5) The switching circuit includes an address discrimination circuit that discriminates the value of the address signal and generates a switching signal, and an output signal of the first circuit or an output signal of the second circuit in response to the switching signal. and a selection circuit for switching and selecting the musical tone waveform generator according to claim (4). (6) The address discrimination circuit includes a detection circuit that detects when the value of the address signal reaches a predetermined address value that is a switching target value, and forms the switching signal in response to the output of the detection circuit. A musical sound waveform generator according to claim (5) of the utility model registration claim. (7) The address discrimination circuit includes a counter that is reset to an initial value in synchronization with the start of musical waveform generation and starts counting from the initial value at a speed sufficiently slower than the rate of change of the address signal; The musical sound waveform generating device according to claim 5, further comprising a comparison circuit for comparing a count value and the address signal, and forming the switching signal in response to a matching output of the comparison circuit.