JPH0715030Y2 - Tuning device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a tuning device for tuning an instrument.

[Background of the Invention] Various tuning devices have been developed conventionally. In this type of tuning device, the string vibration of a picked-up guitar or the like is converted into an electric signal, pitch is extracted from the electric signal, and the result is compared with the internally stored basic pitch data. Is generally displayed to inform the operator.

However, in this type of conventional tuning device, for example, 6
When tuning each string, it is necessary to previously specify the string to be played by switch operation and switch the data of the basic pitch before performing tuning, which makes the operation complicated.

[Object of the Invention] The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a tuning device having good operability when tuning a plurality of strings.

SUMMARY OF THE INVENTION The present invention has been made to achieve the above object, and a plurality of strings, a plurality of string vibration detecting means for independently detecting the vibration of each of the strings, and the string vibration detecting means. Frequency detecting means for detecting the frequency of the string vibration, storage means for storing a plurality of reference period data respectively corresponding to the frequencies to be tuned for each string, and the string vibration detecting means for detecting the string vibration. The reference period data corresponding to the string is read from the storage unit, the reference period data read by the reading unit, and the reference period data detected by the string vibration detecting unit is detected. The main point is to have a comparison means for comparing the string vibration frequency of the string vibration detected by the frequency detection means and displaying the comparison result.

[Embodiment of the Invention] Hereinafter, one embodiment of the present invention will be described in detail 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. That is, in this embodiment, the guitar body has a pitch extraction circuit section and a tuning circuit section.

In the figure, reference numeral 1 denotes the pitch extracting circuit for the first string, and the second to sixth strings are exactly the same, so only the pitch extracting circuit 1 for the first string is shown 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. The output of the pickup 11 is the filter 12 (low pass filter).
Is applied to the higher order harmonic signals to remove them.
It is desirable that the cutoff frequency of the filter 12 be set to be different for each string in accordance with the range of the vibration frequency being different for each string.

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

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

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 chain line). Four
Given through. The voltage level 1/2 Vcc is also applied to the + terminal of the operational amplifier 14-3. Above resistor
It is desirable that the resistance ratio of 14-2 and 14-4 is about 10: 1.

The output of the operational amplifier 14-3 is inverted and output by the inverter 14-5, and is given to the 1/2 frequency divider 15 in FIG.
In addition, the zero cross comparator 14 of FIG.
It is one example circuit, and other circuit modifications are possible.

The 1/2 divider 15 inverts the output level every time the output of the inverter 14-5 of the zero-cross comparator 14 rises, that is, every time the signal falls, and divides the frequency by 1/2. The output of the / 2 frequency divider 15 is a CPU 100 including a microprocessor for controlling the overall circuit operation of this embodiment.
Is supplied to the A counter 16 and directly to the B counter.
It is supplied to 17 via an 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. That is, the time interval between the zero cross points of the waveform signal obtained by dividing the vibration waveform by 1/2 is measured. Then, the measurement operation is stopped by the fall of the applied voltage, and the content is held until the next counting time.

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

Then, the count values of the A counter 16 and the B counter 17 are
It is supplied to the CPU 100.

Reference numeral 19 in FIG. 1 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) is obtained and each signal is supplied to the CPU 100.

Details of the peak position and the envelope detection circuit 19,
As shown in FIG. 3, the signal from the filter 12 is supplied to the + terminal of the operational amplifier 19-1, and the output of the operational amplifier 19-1 is applied to its-terminal through the diode 19-2. , And is given to one end of the capacitor 19-4 via the resistor 19-3.

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

The output of the operational amplifier 19-1 is given to the-terminal of the operational amplifier 19-7 via the resistor 19-6. Also, the resistor 19
-6 is connected to the voltage level 1/2 Vcc through the resistor 19-8, and the voltage level 1/2 Vcc is also connected to the + terminal of the operational amplifier 19-7. It is desirable that the resistors 19-6 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. The voltage level 1/2 Vcc is applied to the + terminal. And the output of this operational amplifier 19-9 is a resistor
It returns to the-terminal via 19-10 and the resistor 19-11.
Is output as an envelope signal via. In addition,
The peak position and envelope detection circuit 19 of FIG.
Is one example circuit, and other configurations may be adopted.

The envelope signal is time-division multiplexed by the CPU 100 as will be described later, is given to the A / D converter 7, is converted into a digital signal, and is then subjected to sound generation start processing.
It is used in various processes such as muffling start process.

This A / D converter 7 performs an analog-digital conversion process on a given analog signal and then sends an A / D end signal to the CPU.
Supply to 100. The CPU 100 accepts this A / D end signal as normal processing in the processing of the main routine. Alternatively, it may be accepted by interrupt. Details are as described later. In addition, this A / D converter 7 is CPU100
It may be a separate chip or 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 reference period table, which is for performing an action peculiar to the present case. That is, the reference cycle table 9 stores cycle data representing a pitch serving as a reference for each string for tuning, which will be described later, and outputs corresponding cycle data in response to a read command from the CPU 100.

Also, TUSW in the figure is a tuning switch, which switches the tuning of this electronic string instrument. That is, this switch
TUSW will allow four mode switching, the frequency of the sound A ₄
By setting 440Hz, 441Hz, 442Hz, 443Hz, the tuning of all scales is determined.

In addition, LED1 and LED2 are the first consisting of light emitting diodes,
The second display element is connected to the CPU 100 via a resistor R, respectively. The character "# (sharp)" is attached near the panel of the guitar body where the first display element LED1 is provided, and similarly "b (flat)" corresponding to the second display element LED2.
Is attached.

The lighting and extinguishing states of the respective display elements LED1 and LED2 are as described later, and it is necessary to clearly indicate whether or not the tuning state of the strings stretched on the body, that is, the tension of the strings is appropriate. become.

The CPU 100 is also connected to the MIDI interface 10. This MIDI is Musical Instrument Digital Int
Abbreviation of erface, 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, via the MIDI interface 10, to the external sound source module 200, which is a sound source unit outside the guitar, outputs a sounding control command, a mute control command, and a pitch change command,
Instructing the external tone generator module 200 to generate musical tones in accordance with the performance operation of strings and frets.

★★ Operation of pitch extraction circuit ★★ Next, the operation of the pitch extraction circuits 1 to 6 of the present embodiment will be described.

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

The output of the zero-cross comparator 14 that is inverted every time the vibration waveform passes through the zero-cross point is divided by the 1/2 divider 15, and the A counter 16 and the B counter 17 count as described above for each change in the output level. The operation is performed alternately.

Then, when the peak point of the vibration waveform is detected by the peak position and the envelope detection circuit 19, the measured counter value is added as necessary in 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 CPU100.

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

FIGS. 4 and 5 show internal timing charts of the pitch extraction circuit 1. When the waveform signal shown in FIG. 4 does not include overtones, the waveform signal is output through the filter 12, and FIG. Shows the operation of each part when the waveform signal when the second harmonic is included is being output through the filter 12.
For overtones higher than that, filter 12 and filter amplifier
Removed at 13. Therefore, the zero-cross comparator 14
A waveform signal containing a fundamental wave representing vibration or a harmonic wave shape up to a second harmonic is given to.

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 each time a voltage signal of a level exceeding the charging voltage of the capacitor 19-4 is given, an operational amplifier 19-1, a diode 19-2, a resistor 19-3. The capacitor 19-4 is charged through the capacitor 19-4, and when the peak position is passed, the capacitor 19-4 is discharged through the resistor 19-5.
The output voltage of is as shown in FIG. 4 and FIG.

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

Further, due to the 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 becomes the peak position signal shown in FIG.

Furthermore, the output signal of the filter 12 is the filter amplifier 13
At, the level is inverted, filtering and amplification are appropriately performed, and the result is given to the zero-cross comparator 14.
The output of the capacitor 14-1 (see FIG. 2) inside the zero-cross comparator 14 is as shown in FIG. 4 and FIG.

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 the figure, the inverted output of this signal is
-Supplied from -5.

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

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

Therefore, when the waveform signal containing only the fundamental wave as shown in FIG. 4 is given from the filter 12, as can be understood from FIG.
Only one of the counters 17 measures once. Therefore, the CPU 100 reads the output of each counter after the measurement is completed, and at the time of peak detection, the counter value detected from the previous peak to the current peak, or one value in the case of FIG. 4,
It will be the period of the fundamental wave 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.

Now, when a waveform signal containing overtones as shown in FIG. 5 is given from the filter 12, as can be understood from FIG.
Both of them will alternately measure once.

Therefore, in CPU100, the counting contents of each counter is
The output signal of the frequency divider 15 is read every time it is inverted, and when the peak position is detected, the counter value detected from the previous peak to the current peak, that is, the two counter values of the A counter 16 and the B counter 17 are added. Then, it becomes the period of the fundamental wave.

★★ Overall circuit operation, especially CPU operation ★★ 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 processing of reading the count values of the A counter 16 and the B counter 17 for each string and the AD conversion processing of the envelope signal are mainly performed.

That is, step S1 is a routine for initial setting after power-on, and in this step S1, initial setting of registers inside the CPU 100, buffer memory 8 and the like is performed.

Next, in steps S2 to S4, the first-string A counters 16 and B
This is a routine to read the contents of the counter 17,
In step S2, it is judged whether the envelope value of the first string exceeds the threshold value. The envelope value is a value obtained by converting the peak position and the envelope signal output of the envelope detection circuit 19 into a digital value by the A / D converter 7. In addition, the A / D of the envelope signal of each string
The conversion order and the like 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 S5.

If the string continues to vibrate after being repelled, the process proceeds from step S2 to step S3, and the output of the 1/2 frequency divider 15, that is, the output of FIGS. 4 and 5 is inverted. It detects whether or not.

If NO is determined in step S3, the process proceeds to step S5 without any processing. If YES is determined in step S3, the A counter 16 or the B counter is determined in step S4.
The CPU 100 reads the contents of 17 and transfers and stores them in the buffer memory 8.

In this case, 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, as described above.

Then, the reading processing of the A counter 16 and the B counter 17 of the first string ends, and the process proceeds to step S5. In step S5, the same processing as that of the first string (steps S2 to S4) is performed for each of the second to sixth strings, and step S6 is performed.
Go to.

In step S6, it is judged whether the A / D end signal has already been given from the A / D converter 7 and the AD conversion of the vibration envelope of the selected string has been completed.

If NO, the process returns to step S2, the steps S2 to S5 are executed, and the step S6 is checked again.

Then, if YES is determined in this step S6,
In step S7, the AD-converted digital signal is
CPU100 accepts as the envelope signal value of the selected string,
The data is stored 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 S5 described above.

Next, in step S8, AD conversion of the next string is started. 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, returning to step S2 following step S8,
Similarly, the processing of the main routine is repeated.

Next, the interrupt processing 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 comes to have a positive peak position (see FIGS. 4 and 5).
(See the drawing), the CPU 100 temporarily interrupts the processing of the main routine, and first performs the processing of step T1.

In step T1, the CPU 100 determines whether the count value of the A counter 16 or the B counter 17 already read in step S4 is
Pitch extraction is performed by adding appropriately.

That is, data representing the time of one cycle is obtained by adding the values of the counter read from the previous peak to the current peak. In this case, in the example of FIG. 4, the count value of one of the A counter 16 or the B counter 17 is 1
This corresponds to one cycle, and in the example of FIG. 5, the added value of the counting results of the A counter 16 and the B counter 17 corresponds to one cycle.

Next, in step T2, a scale table (which is a series of data recorded in the internal memory of the CPU 100 and showing the relationship between the cycle and the scale (for example, in semitone units)) is searched to obtain scale information.

In step T3, it is judged whether or not the scale information obtained as a result of the pitch extraction processing as described above matches a predetermined number of times.
In this case, it is the earliest to compare and compare the extraction cycles of two times to determine the scale and improve the responsiveness. However, by detecting the number of matches more than that, it is possible to improve and stabilize the frequency accuracy. Will be able to.

If YES is determined in step T3, next step T4
At, sound control and frequency change control are performed. That is, the tone generation command of the musical tone of the corresponding pitch is output to the external tone generator module 200 via the MIDI interface 10.

Then, after performing the processing of storing the scale information designating the pitch of the generated musical tone in this step T4, 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 T4, the generation control of the musical sound of the pitch is controlled by the external sound source module. Performed for 200.

In addition, after the start of sound generation, at the time of this interrupt processing, a frequency change command is issued to the MIDI interface
It is sent to the external sound source module 200 via 10 and the pitch change control is performed according to the frequency change of the string vibration. When the string vibration is dampened, mute control is also performed at this step T4.

★★ Tuning operation ★★ Next, the tuning operation, which is the characteristic operation of this case, will be described.

The tuning interrupt flow of FIG. 6 is executed by a timer interrupt during the main flow operation. For example, this interrupt is performed every 4 ms. Of course, similar processing may be executed in the main routine.
Those are optional matters.

By the way, first, in step W1, it is judged whether or not there is only one string being sounded. This may be detected by reading out the number of the string for which the sounding operation control is performed in step T4 described above from the buffer memory 8.

Then, if only one string is vibrating, proceed to step W2, and for the O-fret scale (open string scale) of that string
The reference period data having a pitch of 550 cents higher is read from the reference period table 9 (see FIG. 1).

Here, the recording data of the reference period table 9 will be described. FIG. 7 shows a storage state of periodic data corresponding to four tuning states of six strings. That is, the reference cycle table 9 has 24 small tables.

That is, as the small table of the reference period of the first string, there are four small tables corresponding to A ₄ = 440 Hz, 441 Hz, 442 Hz, and 443 H1 which the tuning switch TUSW can switch for the open string scale E ₄ . This small table is E ₄ +55
Periodic data of 0 cent, E ₄ +3 cent, and E ₄ -3 cent are stored respectively. The same applies to the other strings.

Of course, for storage capacity reduction, the cycle data of the "open string scale +550 cents" when the A ₄ = 440 Hz, other tuning state _{(A 4 = 441Hz, 442Hz,} 443Hz) if to use any 1 The type will improve. Even if it does in this way, the problem does not actually occur.

Now, in step W2, the periodic data corresponding to the O fret +550 cents in the specific small table determined from the string number and the operating position of the tuning switch TUSW is read out.

Next, in step W3, the vibration cycle of the string (which has already been obtained for the string in step T1) is compared with the cycle selected as described above. Then, if the vibration cycle is smaller than the reference cycle of the open string scale +550 cents (the pitch is high), in step W4, it is doubled with the desired vibration frequency and the value obtained as a result, The same comparison is again made with the reference period described above (step W5), and if the result is YES, the value of the period is doubled again in step W6 (which means that the original oscillation period has been multiplied by 4). ). If steps W3, W5
If the determination is NO, the process proceeds to step W7. FIG. 8 shows this state by focusing on the first string.

For the 1st string, the open string scale is E ₄ , so the open string +550
The pitch of the cent is midway between A ₄ and A ₄ ^#, and it is doubled when extracting the vibration cycle of the pitch exceeding it, and further, the open string + 1750 cents (this is the value of A ₅ and A ₅ ^# It becomes 4 times when extracting the vibration period of the pitch exceeding the middle). In other words, the obtained vibration period is changed by the octave so that it matches the octave period of the open string.

And. In steps W7 and W8, a comparison is made between the extraction period for which the octave change control is performed and the reference period of open string scale ± 3 cents. Of course, this reference cycle data is
It is obtained by reading from a specific small table of the reference cycle table 9 shown in FIG.

Then, if YES in step W7, the flow proceeds to step W9 to set the output to 0, if NO in step W8, sets the output to 1 in step W10, and if YES in step W8 outputs 2 in step W11.
And

As a result, as shown in FIG.
The output is 1 if the extraction period is within 3 cents, and 2 if the pitch is higher than the 3 cent treble with respect to the open string scale.
When the open string scale is lower than 3 cent bass, the output becomes 0.

Then, in step W12, this output is added to the register SUM in the CUP 100, and in step W13, judgment is made based on the value of the number of times counter in the CPU 100 whether this loop has been passed 16 times. This value of "16" is not particularly significant. In order to guarantee the stability of the cycle extraction and prevent the extraction error, it is only repeated a plurality of times.

If NO, return to the main routine. If YES, the values of the register SUM are compared in the next steps W14 and W15.

The comparison values 8 and 23 of steps W14 and W15 are outputs 0, 1, and
If you think about what the value will be when 2 is repeated 16 times, you can understand its meaning. The judges in steps W14, W15 and step W1 confirm the following conditions, and as a result, determine the display states of the two display elements LED1 and LED2.

i) Only the first display element LED1 is turned on (step W16) ....
When the extracted pitch is higher than the reference pitch + 3 cents (the cycle is short).

ii) Only the second display element LED2 lights up (step W17) ....
When the extracted pitch is lower than the standard pitch-3 cents (long cycle).

iii) Both the first and second display elements LED1 and LED2 are turned on (step W18) ... The extracted pitch is the reference pitch +3.
When it is between the cent and the standard pitch-3 cents, that is, when the extracted pitch substantially matches the basic pitch.

iv) Both the first and second display elements LED1 and LED2 are turned off (step W19) ... When multiple strings are vibrating at the same time, or no strings are being vibrated and no strings vibrate. .

Then, after the driving operation for these display elements LED1 and LED, the register SUM is cleared in step W20, and the frequency counter inside the CPU 100 is reset. Then return to the main flow.

By this flow processing of tuning interrupt,
So-called octave tuning can also be performed as shown in FIG. In other words, in addition to open strings, picking on the 12th fret and even the 24th fret will be compared with the reference pitch within the specified range (eg ± 3 cents) without any special operation. The display modes of the display elements LED1 and LED2 change according to the result.

As described above, in the present embodiment, the tuning display is performed by the two display element LEDs by simply operating the strings for each of the six strings.
It can be done with 1 and LED2 and has good operability.

Moreover, it is more convenient because the value of the reference pitch to be compared is switched and selected when the tuning switch TUSW is switched.

Further, it is convenient because it is possible to know for each string whether or not the tension of the string is correct only by providing the two display elements LED1 and LED2. In particular, since the lighting drive is not performed at the time of operating a plurality of strings, the operator tunes while separating each string (of course, it is normal to make such an adjustment when tuning). It is not necessary to provide a separate display for displaying which string has been tuned, etc., which is good in terms of productivity and cost.

Although one embodiment has been described in detail above, the present invention can be applied in various modifications.

That is, in the above example, the cycle extracted in steps W4 and W6 is doubled.
Even if it is doubled and the extraction cycle is not changed, the same effect can be obtained. Octave tuning is possible with either method.

Further, in the above example, the tuning switch TUSW can be used to perform four switching operations, but it may be continuously variable. In such a case, the contents of the reference cycle table 9 can be rewritten and the CPU 100 It can be realized by rewriting with calculation etc.

In the above example, the threshold pitch is ± 3 cents with respect to the reference pitch, and the pitch is compared with the extracted pitch.

In addition, as shown in FIG. 8, open strings (O frets) +
The display mode is switched at 550 cents and open string + 1750 cents, but the division position of this can be variously changed.

Further, in the above embodiment, the tuning display is always performed by the two display bodies LED1 and LED2, but the tuning mode and the normal performance mode are switched by a switch or the like so that such a display is performed only at the time of tuning. You may Also, at least two displays are required,
It may be more than that.

Further, in the above-described embodiment, the present invention is applied to the electronic guitar having the body provided with six strings, but it is also applicable to the guitar and other types of electronic string musical instruments regardless of the integrated type or the separate type. .

Further, in the above embodiment, the zero cross comparator
Although the pitch is extracted by the period data based on the detection of the zero-cross point by 14, the pitch may be extracted by a method other than that, for example, by detecting the interval between the maximum peak values.

[Effects of the Invention] As described in detail above, according to the present invention, tuning of a plurality of strings can be performed without performing a switching operation of switches or the like for each string. That is, the reference cycle data corresponding to the string in which the vibration is detected is read out and compared with the frequency of the detected string vibration. Therefore, it is convenient because it does not require a switching operation such as a switch operation according to the number of the string to be tuned.

[Brief description of drawings]

FIG. 1 shows 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. And 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. Is a diagram showing the contents of the reference cycle table, and FIG. 8 is a diagram showing the operating state of the same embodiment. 1-6 ... Pitch extraction circuit, 7 ... A / D converter, 9
…… Reference cycle table, 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, TUSW ... Tuning switch, LED1 ... First display element, LED2 ...
... Second display element.

Claims (1)

[Scope of utility model registration request] 1. A plurality of strings, a plurality of string vibration detecting means for independently detecting the vibration of each string, a frequency detecting means for detecting a frequency of the string vibration detected by the string vibration detecting means, Storage means for storing a plurality of reference period data respectively corresponding to the frequencies to be tuned for each string; and the reference period data corresponding to the strings for which the string vibration detection means has detected the string vibration, from the storage means. The reading means for reading, the reference cycle data read by the reading means, the string vibration detecting means detects the string vibration, and the string corresponding to the reference cycle data is detected by the frequency detecting means. And a comparison means for comparing the frequency of the string vibration and displaying the comparison result.