JP2560327B2 - Electronic string instrument - Google Patents

Description

TECHNICAL FIELD OF THE INVENTION The present invention relates to an electronic stringed instrument such as an electronic guitar and a guitar synthesizer.

[Prior Art and its Problems] Various types of guitar-type electronic musical instruments have been conventionally developed. One of the important things in this kind of electronic stringed instrument is that it picks up the vibration of each string electrically, extracts the period (pitch) of the fundamental wave of this string vibration quickly, and outputs it to the sound source device. It is to send a musical tone command.

If it takes a long time from the occurrence of string vibration caused by picking to the start of the output sound, it will be very inconvenient and uncomfortable for the performer.

Therefore, it has been necessary to improve the responsiveness when the musical tone is generated by detecting the string vibration and extracting the pitch.

[Object of the Invention] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an electronic stringed instrument that has a good responsiveness at the start of sounding.

SUMMARY OF THE INVENTION That is, the present invention has been made in order to achieve the above-mentioned object, and a vibration of a string is started by a picking operation or the like, and any one of detection means provided corresponding to each string is an electric signal. For a predetermined period from the time when it is detected that the output level of the above exceeds a predetermined level, it is necessary to instruct the other strings for which the sounding instructing means is instructed to sound to stop the pitch extraction. The point is.

[Embodiment] An embodiment of the present invention will be described in detail below with reference to the drawings.

★★ Structure ★★ FIG. 1 shows the entire circuit structure of the embodiment, showing the structure inside the body of a guitar-type electronic string instrument and the structure of the external circuit connected thereto.

In the figure, reference numeral 1 denotes a pitch extracting circuit for the first string, and a second string to a pitch extracting circuit.
Since the sixth string is exactly the same, only the pitch extracting circuit 1 of the first string is shown in detail in the drawing.

Reference numeral 11 is a pickup, which converts the vibration of the first string into an electric signal. That is, in this embodiment, the independent pickup is provided for each of the six strings. Then, the output of the pickup 11 is applied to the filter 12 (low-pass filter) so that the higher-order overtone signal is removed. It is desirable that the cutoff frequency of the filter 12 be set to be different for each string according to the range of the vibration frequency for each string.

The output of the filter 12 is applied to a filter amplifier 13, further appropriately filtered and amplified, and applied to a zero cross comparator 14.

The details of the zero-cross comparator 14 are as shown in FIG. 2, in which the output of the filter / amplifier 13 is given to the capacitor 14-1 and becomes a signal, after which the operational amplifier 14− is supplied via the resistor 14-2. 3 is applied to the-terminal.

A voltage of 1/2 Vcc is applied to the resistor 14-2 as a center voltage level (the center level in the timing charts of FIGS. 4 and 5 which will be described later and is indicated by a dashed line).
Given through 14-4. In addition, the above voltage level 1/2 Vcc
Is also given to the + terminal of the operational amplifier 14-3. The resistance ratio of the resistors 14-2 and 14-4 is preferably about 10: 1.

The output of the operational amplifier 14-3 is the inverter 14-5.
It is inverted and output at and is given to the 1/2 frequency divider 15 in FIG. The Xerox comparator 14 shown in FIG.
Is an exemplary circuit, and other circuit modifications are possible.

This 1/2 frequency divider 15 inverts the output level every time the output of the inverter 14-5 of the Xerox comparator 14 rises, that is, every time the signal falls, and divides the frequency by 1/2. The output of the 1/2 frequency divider 15 is the CPU 1 including a microprocessor for controlling the overall circuit operation of this embodiment.
The signal is supplied to the A counter 16 directly and to the B counter 17 via the inverter 18.

The A counter 16 and the B counter 17 are initialized when the respective applied signals rise, and count the clock pulse CLK only during the high level. In other words, the vibration waveform
The time interval between the zero cross points of the waveform signal obtained by frequency division is measured. Then, the measurement operation is stopped by the fall of the applied voltage, and the contents are held until the next counting.

Therefore, in this embodiment, the A counter 16 and the B counter 17
Measure the time intervals between the respective zero-cross points alternately.

The count values of the A counter 16 and the B counter 17 are supplied to the CPU 100.

In FIG. 1, reference numeral 19 denotes a peak position and envelope detection circuit which detects the peak position (positive maximum level position) of the output voltage signal of the filter 12 and obtains an envelope signal obtained by connecting the peak positions. (Envelope signal) and supplies each signal to the CPU 100.

The details of the peak position and envelope detection circuit 19 are shown in FIG. 3, and the signal from the filter 12 is
This operational amplifier is supplied to the + terminal of operational amplifier 19-1.
The output of 19-1 is applied to its negative terminal via diode 19-2 and the capacitor via resistor 19-3.
It is given at one end of 19-4.

The voltage level 1/2 Vcc is applied to the other end of the capacitor 19-4. Therefore, the diode 19-2
Will be charged only during the period when the voltage signal applied via the capacitor 19-4 is higher than the charge voltage of the capacitor 19-4, and will be discharged through the resistor 19-5 during the other period.

The output of the operational amplifier 19-1 is given to the-terminal of the operational amplifier 19-7 via the resistor 19-6. Further, the resistor 19-6 is connected to the voltage level 1 / via the resistor 19-8.
It is connected to 2 Vcc, and the voltage level 1/2 Vcc is also connected to the + terminal of the operational amplifier 19-7. This resistor 19-
It is desirable that 6 and 19-8 have the same resistance value. The output of the operational amplifier 19-7 becomes a signal indicating the peak position and is supplied to the CPU 100.

The output of the resistor 19-5 is given to the-terminal of the operational amplifier 19-9, and the positive terminal thereof has the voltage level 1/2 Vcc.
Is given. The output of the operational amplifier 19-9 is returned to the-terminal via the resistor 19-10,
It is output as an envelope signal via the resistor 19-11. The peak position and envelope detection circuit 19 shown in FIG. 3 is one example circuit, and may have other configurations.

The envelope signal is time-division-multiplexed by the CPU 100 as will be described later and is given to the A / D converter 7 and converted into a digital signal, after which various processes such as sound generation start processing and mute start processing are performed. Used in.

The A / D converter 7 performs analog-digital conversion processing on the supplied analog signal and then outputs an A / D end signal to C
Supply to PU100. The CPU 100 accepts this A / D end signal as a normal process in the process of the main routine, or accepts it by an interrupt. Details are as described later. This A / D converter 7 is a CPU
It may be a chip separate from 100 or may be an A / D converter inside a one-chip microcomputer.

The CPU 100 executes various processes in cooperation with the buffer memory 8. Further, reference numeral 9 in FIG. 1 is a frequency counter, which is for performing an action peculiar to the present case. That is, when the CPU 100 detects that the number of vibrations of any one of the plurality of strings has changed from being below the predetermined level to being above the predetermined level for the first time, the number-of-times counter 9 is set to a predetermined value. The number of times of skipping is performed so as to extract the period of the fundamental wave of only the vibration of the string and not to extract the period of the fundamental wave of the vibration of other strings. As a result, the pitch at the start of vibration of the picked strings can be concentratedly extracted.

The CPU 100 is connected to the MIDI interface 10. This MIDI is Musical Instrument Digital I
Abbreviation for nterface, which is a unified standard for connecting musical instruments and personal computers with musical instruments. Of course,
An interface using a format other than this MIDI format may be used.

Then, through this MIDI interface 10, a tone generation control command, a mute control command, and a pitch change command are output to an external tone generator module 200, which is a tone generator section outside the guitar, and the pitch and fret playing operations are performed. , And instructs the external sound source module 200 to generate a musical sound.

★★ Operation of Pitch Extraction Circuit ★★ Next, the operation of the pitch extraction circuits 1 to 6 of this embodiment will be described.

Before describing the details, the basic method of pitch extraction according to the present embodiment will be described first.

The output of the zero-crossing comparator 14, which is inverted every time the vibration waveform passes through the zero-crossing point, is frequency-divided by the 1/2 frequency divider 15, and each time the output level changes, the A counter 16 and the B counter 17
And alternate counting operations as described above.

When the peak point of the vibration waveform is detected by the peak position and envelope detection circuit 19, the measured counter value is added as necessary during the time from the previous peak point to the current peak point. Then, the time length of one cycle of the waveform is calculated. This calculation is performed by the CPU 100.

Therefore, the period of the fundamental wave of the string vibration generated by picking or the like can be extracted from two or one of the count values of the A counter 16 and the B counter 17.

FIGS. 4 and 5 show timing charts inside the pitch extracting circuit 1. FIG. 4 shows a timing chart when the waveform signal containing no overtone is output via the filter 12.
FIG. 5 shows the respective operations of the respective parts when the waveform signal containing the overtone is output through the filter 12. The overtones higher than that are removed by the filter 12 and the filter amplifier 13. Therefore, the zero-cross comparator 14 is supplied with a waveform signal including a fundamental wave representing vibration or a harmonic waveform up to a second harmonic.

FIGS. 4 and 5 show the output of the filter 12 of FIG. Then, this waveform signal is given to the peak position and envelope detection circuit 19, and the capacitor 19-4
Each time a voltage signal of a level exceeding the charging voltage of is given, the operational amplifier 19-1, diode 19-2, resistor 19-
3, the capacitor 19-4 is charged with electric charge, and when it passes the peak position, it is discharged through the resistor 19-5. As a result, the output voltage of the capacitor 19-4 is as shown in FIGS.
As shown in the figure.

Therefore, the envelope signal output via the operational amplifier 19-9 and the resistor 19-11 is as shown in FIGS.

Further, due to a change in the output of the operational amplifier 19-1, the operational amplifier 19-7 falls at the start of charging the capacitor 19-4 and at the end of charging, that is, at the positive peak position of the vibration waveform. The signal shown in FIG. 5 is output. This is the peak position signal shown in FIG.

Further, the output signal of the filter 12 is
At 13, the level is inverted, and appropriate filtering and amplification are performed, and the result is given to the zero-cross comparator 14. Zero-crossing comparator 14 internal capacitor 14−
The output of 1 (see FIG. 2) is as shown in FIGS. 4 and 5.

Then, the level of this signal is inverted every time it passes through the zero cross point via the operational amplifier 14-3.
As shown in FIG. 5, the inverted output of this signal is supplied from the inverter 14-5.

Therefore, the A counter 16 is reset when the output (FIGS. 4 and 5) obtained by dividing the signal by the 1/2 frequency divider 15 rises, and measures the clock signal CLK until the signal is inverted. Then, after the measurement is completed, the measured value is held.

The B counter 17 performs a counting operation reverse to that of the A counter 16. That is, the B counter 17 is reset when the signal falls, and measures the clock signal CLK until the signal is inverted. Then, after the measurement is completed, the measured value is held.

Accordingly, when a waveform signal containing only the fundamental wave as shown in FIG. 4 is given from the filter 12, FIG.
As can be understood from FIG. 7, only one of the A counter 16 and the B counter 17 measures once in one cycle of the waveform. Therefore, the CPU 100 reads the output of each counter after the end of the measurement, and when the peak is detected, the counter value detected from the previous peak to the present peak, and one value in the case of FIG.
The cycle of the fundamental wave is used as it is.

In addition, in order to improve the accuracy of pitch extraction and prevent malfunctions due to noise, etc., only when a match with the pitch extracted the previous time or before is detected and a match within a predetermined error range is detected, It is desirable to determine the vibration frequency. If the pitches are determined by performing coincidence comparisons of a plurality of extraction periods, the responsiveness at the start of picking becomes a problem. In the present embodiment, such a case will also be described later. You can deal well with the reason.

Now, when the waveform signal including the overtone as shown in FIG. 5 is given from the filter 12, as can be understood from FIG.
Both of the seventeen will alternately measure once each.

Therefore, in the CPU 100, the count content of each counter is calculated as 1 /
It is read every time the output signal of the frequency divider 15 is inverted, and when the peak position is detected, the counter values detected from the previous peak to the current peak, and therefore the A counter 16 and the B counter 17
Are added to obtain the period of the fundamental wave.

★★ Overall Circuit Operation, Especially Operation of CPU ★★ Next, the overall circuit operation of this embodiment will be described in detail.

FIG. 6 is a flowchart showing the operation of the CPU 100. In the main routine, the A counter 16 and the B counter 17 are used.
Reading the count value of each string and the AD of the envelope signal
The conversion process is mainly performed.

That is, step S1 is a routine for initializing after power-on, and in this step S1, the internal registers of the CPU 100, the buffer memory 8, the frequency counter 9, etc. are initialized.

Next, in steps S2 to S6, the A counter 16 of the first string,
This is a routine for reading the contents of the B counter 17, and in step S2, it is judged whether or not the envelope value of the first string has exceeded a threshold value. The envelope value is a value obtained by converting the envelope signal output of the peak position and envelope detection circuit 19 into a digital value by the A / D converter 7. The order of the A / D conversion of the envelope signal of each string will be described later.

Then, in this step S2, when it is detected that the envelope of the first string does not exceed the threshold value (that is, the vibration level is small), it is determined that the string is not picked, and NO is determined. Proceed to step S7.

If the string continues to vibrate after being repelled, the process proceeds from step S2 to step S3 to judge whether the number counter 9 is 0 or not. The number counter 9 is set to an initial value other than 0 when any string is newly picked. If a certain period has passed since the start of the string vibration, the content of the number counter 9 becomes 0 as described later.

Therefore, when the number counter 9 is other than 0, that is, when the value is equal to or less than the initial value and is 1 or more, the CPU 100 determines NO, and in the next step S4, the relevant string (first string in this case).
The external sound source module
At 200, judge whether or not the pronunciation is continued. If YES is determined, it is determined that the pitch extraction processing of the string is not urgent, and the steps S4 to S7 are performed.
Go to.

Then, if NO is determined in step S4 or YES is determined in step S3, the process proceeds to step S5, and the output of the 1/2 frequency divider 15, that is, the output of FIG. 4 is inverted. To detect.

If NO is determined in step S5, the process proceeds to step S7 without any processing. If YES is determined in step S5, the contents of the A counter 16 or the B counter 17 are changed in step S6. The CPU 100 reads and transfers and stores it in the buffer memory 8.

In this case, as described above, the CPU 100 reads the contents of the A counter 16 when the signal falls, and reads the contents of the B counter 17 when the signal rises.

Then, the reading processing of the A counter 16 and the B counter 17 of the first string is completed, and the process proceeds to step S7. In step S7, the same processing as that of the first string (steps S2 to S6) is performed for each of the second to sixth strings, and
Proceed to S8.

In step S8, it is judged whether the number counter 9 is 0 or not. If it is not 0, the process proceeds to step S9, the content is down-counted, and then the process proceeds to step S10. If yes
If so, go to step S10 without processing anything. Therefore, if the number counter 9 is other than 0, it is down-counted by 1 each time the main flow is executed once.

Then, in step S10, either the A / D conversion end signal of the A / D converter 7 is accepted by an interrupt (interrupt) and the subsequent processing is executed or controlled, or after step S10, normal processing is performed and AD conversion is performed. Select whether to perform the process.

In this case, if the A / D conversion end signal is received by interruption and processed, AD conversion of the envelope signal of each string can be performed at high speed. That is, the A / D converter 7 performs AD conversion of the envelope signals of the strings one after another without any rest time. For example, when the start of vibration of one string is detected, there is a high possibility that other strings will be picked at the same time, and an interrupt (interrupt) after AD conversion is accepted.
Return from 0 to step S2, and then step S2 of the main routine
The acceptance of the interrupt processing in step S9 is permitted.

If the AD conversion interrupt is masked, the process proceeds to step S11 following step S10, and the A / D converter 7
The A / D end signal has already been given from, and it is judged whether or not the AD conversion of the envelope of the vibration of the selected string is completed.

If NO, the process returns to step S2, the steps S2 to S10 are executed, and the step S11 is checked again.

If YES is determined in step S11, the process proceeds to step S12, in which the CPU 100 accepts the AD-converted digital signal as the envelope signal value of the selected string and stores it in a predetermined area of the buffer memory 8. . This envelope value is used in the steps corresponding to step S2 in step S2 and step S7 described above.

Then, following step S12, in step S13, it is determined whether new picking has been performed or based on the extracted envelope value, that is, it is determined whether or not the predetermined threshold level is exceeded, and if YES, step S14 Then, the process proceeds to step S9 and sets a predetermined value in the frequency counter 9. As described above, the number of times corresponding to the set value is newly added to the string vibration, the counter reading process for the string before the start of sound generation (step S6) and the pitch extraction and sound generation control process (step T3) described later are performed. Will be focused on and the processing for other strings will be skipped.
Strictly speaking, step S6 is YES in step S5.
Since it is executed when the determination is made, the number of times the counter reading process is preferentially executed may be smaller than the value set in the number counter 9.

Following this step S14 or if a NO determination is made in step S13, the flow advances to step S15 to start AD conversion of the next string. That is, in order to AD-convert the envelope signals of the first string to the sixth string, when the AD conversion of the envelope signal of one string is completed, the AD conversion of the envelope signal of the next rank is started.

Then, after returning to step S15, the process returns to step S2, and the processing of the main routine is repeated in the same manner.

Next, the interruption process when the peak position signal output from the peak position and envelope detection circuit 19 arrives will be described.

When this signal rises, the output waveform signal of the filter 12 just takes a positive peak position (see FIGS. 4 and 5), and the CPU 100 temporarily suspends the processing of the main routine, and firstly proceeds to step T1. Is performed.

In step T1, it is determined whether or not the number counter 9 is 0, and if it is not 0, the process proceeds to step T2, and it is judged whether or not a musical sound is being generated corresponding to the string. If YES, then the processing for that string is not urgent and returns to the main routine. If NO in step T2, CP
In step T3, U100 reads the value of A counter 16 or B counter 17 already read in step S6,
If the predetermined condition is satisfied by performing appropriate addition and pitch extraction, the tone generation control process of the musical tone of the corresponding pitch is performed, and a predetermined command is output to the external tone generator module 200 via the MIDI interface 10. Become. in this case,
In step T3, when the pitch at the start of sounding is determined based on the result of a plurality of pitch extractions, the processing of the vibrating string is preferentially performed (that is, the pitch extraction of the strings other than the string and the A counter are performed. The reading process of 16 or B counter 17 is skipped, and the interval for repeating the process for the tone generation start string becomes short.), Which is effective.

If the number counter 9 is 0 after the start of sound generation, a frequency change command is sent to the external sound source module 200 via the MIDI interface 10 in step T3 during this interrupt processing to generate a string vibration. Pitch change control is performed according to frequency changes. When the string vibration is damped,
Mute control is also performed in this step T3. When the envelope becomes equal to or less than the threshold value and the pitch of the same value cannot be continuously extracted, the mute processing is performed.

Then, the process returns to the main routine. Therefore,
In the main routine, while the count value corresponding to the vibration period of each string is detected by the CPU 100, by executing the interrupt processing T1 to T3, the generation control of the musical sound of the pitch is performed by the external tone generator module 200. Is done against.

Each step of U1 to U4 in FIG. 6 shows the details of the interrupt routine when the A / D end signal is received from the A / D converter 7 by interrupt and processed, and the AD interrupt is enabled. This is a process that becomes valid when (the determination in step S10 is NO).

Since the contents of the processing of each step are exactly the same as those of steps S12 to S15 of the above-mentioned main routine, the description thereof will be omitted.

As described above, according to the present embodiment, when a guitar is played, a process for a pitch change of a sound that is already sounded and a sound corresponding to a string that is newly vibrated by picking or the like are generated. The process of starting sound generation is performed by changing the priority order, and it is possible to prevent inconvenience and discomfort in the performance of the performer.

That is, the processing at the start of sound generation can be performed quickly after the detection of string vibration, and the responsiveness at the start of sound generation is improved. For this reason, the processing of changing the frequency of the musical tone being sacrificed at the time of sacrifice is unlikely to cause any particular problem in performance even if the response time is slightly delayed.

In the above embodiment, the present invention is incorporated in the body.
Although it is applied to an electronic guitar provided with three strings, it is also applicable to other types of electronic string musical instruments.

Further, in the above embodiment, the pitch is extracted by the periodic data based on the detection of the zero-cross point by the zero-cross comparator 14, but the pitch is extracted by other methods, for example, by detecting the interval between the maximum peak values. You may.

Further, in the above embodiment, the number of times of processing of the main routine is counted by the number counter 9 to ensure the centralized processing at the start of sound generation, but the same may be done by other means. For example, it is possible to count the time and guarantee the above-mentioned centralized processing for a fixed time.

In addition, in the above embodiment, when the string is newly picked, step S14 or step U in FIG.
In 3, the frequency counter 9 is set to a predetermined value, and the count values of the A counter 16 and the B counter 17 for the strings to be picked and start sounding are read by the number of times corresponding to the value (step S6) and the pitch is set. The calculation process (step T3) for extraction is preferentially executed by not performing the same process for other strings.

However, with a slight change in the processing flow of the CPU 100, it is possible to deal with the re-sound generation start processing when the vibration of the strings is continuously instructed by the tremolo playing method.

That is, for example, in step S13 or step U2 (see FIG. 6), (i) when a non-vibrating string is newly picked and the output level of the corresponding electric signal exceeds a predetermined level, (ii) ) When a string is being vibrated but the output level of the electric signal has decreased due to the vibration after picking, and when the string is picked again and exceeds a predetermined level again. The conditions may be detected respectively, and in each case, the process may proceed from step S13 or step U2 to step S14 or step U3 to preset a predetermined value in the frequency counter 9 as described above.

If the flow is changed, step S
4. In step T2, (i) the string is not vibrating,
Therefore, it detects both that no musical sound is generated, and (ii) that the volume level is below the predetermined value even after the sound is being generated, and then exceeds the threshold value again.
The content of the process may be changed so that NO is determined in steps S4 and T2, and then step S5, S6 or step T3 is executed.

[Effects of the Invention] As described in detail above, according to the present invention, when the output level of the electric signal generated based on the vibration of the strings exceeds a predetermined level, pitch extraction is intensively performed on the exceeded strings. Since the pitch at the start of sounding is promptly determined, the responsiveness at the start of sounding is improved.

Therefore, it is effective when performing according to the arpeggio style.

[Brief description of drawings]

The drawings show an embodiment of the present invention, FIG. 1 is a diagram showing a circuit configuration of the embodiment, FIG. 2 is a detailed circuit diagram of the zero-cross comparator of FIG. 1, and FIG. 3 is a peak position. FIG. 4 is a detailed circuit diagram of the envelope detection circuit, FIGS. 4 and 5 are timing charts showing the operation of the embodiment, and FIG. 6 is a flow chart showing the operation of the embodiment. 1-6 ... Pitch extraction circuit, 7 ... A / D converter, 9
…… Count counter, 14 …… Zero cross comparator, 15
...... 1/2 divider, 16 ... A counter, 17 ... B counter, 19 ... Peak position and envelope detection circuit, 100
…… CPU, 200 …… External sound source module.

Claims (2)

(57) [Claims] 1. A conversion means for converting the vibration of each of a plurality of strings into an electric signal, and a pitch extraction means for sequentially extracting the pitch of the electric signal output from the conversion means for each of the strings. For each of the strings, a detection unit that sequentially detects whether or not the electric signal exceeds a predetermined level, and an output level of the electric signal that corresponds to any vibration of each string by the detection unit has a predetermined value. In the electronic stringed instrument, which has a sounding instructing means for instructing sounding based on the pitch corresponding to the string extracted by the pitch extracting means when it is detected that the string is exceeded, Any one of the detecting means provided to another string for which sound generation is instructed by the sound generation instructing means only for a predetermined period from the time when it is detected that the output level of the electric signal exceeds a predetermined level. To an electronic stringed instrument characterized by comprising control means for controlling the pitch extraction means to an instruction to stop the pitch extraction. 2. The pitch extracting means has envelope extracting means for extracting the envelope of the electric signal based on the vibration of the strings, and the detecting means compares the output envelope of the envelope extracting means with a predetermined value. The electronic stringed instrument according to claim 1, wherein a judgment is made as to whether or not the predetermined value is exceeded.