JP2000267654A - Tempo calculation method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To shorten the tempo calculation time. SOLUTION: In this tempo calculation method, beats are continuously detected and a beat time which is the interval time of the continuously detected beats is continuously detected. in the past M pieces of the beat time (BT1-BT8), the number of the beat time close to the beat time of the present measurement is detected. In a case that the number of the beat time in the past close to the beat time of the present measurement is equal to or more than N, the average beat time of the beat time of the present measurement and the beat time in the past close to the beat time is calculated. As a tempo, the quotient of 60 divided by the average beat time is set. By the above-mentioned processing, the tempo is calculated and the calculated tempo is changed (brought closer) to the actual tempo of music.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a tempo calculation method, and more particularly, to a tempo calculation method for calculating the tempo of music from a sound source.

[0002]

2. Description of the Related Art As shown in FIG. 14, a conventional audio apparatus uses a sound source (for example, a mini-disc recorder 14, a CD player 16, a cassette tape recorder 18, and a tuner 20) to adjust the music tempo. Sound that occurs periodically along the high frequency side (3 kHz to 15 kHz)
And a spectrum analyzer IC 28 for detecting a sound (attack sound) having a predetermined frequency (e.g., 3.4 kHz) and a sound (beat sound) having a predetermined frequency (e.g., 105 Hz) on a low frequency side (100 Hz to 300 Hz). The spectrum analyzer IC 28 includes a microcomputer (hereinafter referred to as a microcomputer 26) and a rhythm dedicated microcomputer 35.
It is connected to the. The operation unit 24 and the display unit 30 are connected to the microcomputer 26. Rhythm dedicated microcomputer 35
Is connected to an audio output IC 32 for selectively outputting a plurality of rhythm patterns formed by combining a plurality of instrument sounds. The audio output IC 32 and the sound source are the amplifier 22
It is connected to the.

[0003] In addition to the microcomputer 28 that controls the display unit 30, the conventional audio apparatus uses an audio signal such that a rhythm pattern is mixed with music from a sound source and output based on the output from the spectrum analyzer IC 28. Output I
A rhythm dedicated microcomputer 35 for controlling C by bidirectional communication is provided. That is, the rhythm dedicated microcomputer 35
Automatically calculates the tempo of the music from the sound source.

In such an audio apparatus, since there are various patterns in the music tempo, the tempo is obtained by matching each pattern and selecting the closest pattern.

[0005]

However, the above-described acoustic device obtains a tempo by matching each pattern and selecting the closest pattern.
Although accurate, it takes a long time to calculate the tempo. The present invention has been made in view of the above facts, and has as its object to propose a tempo calculation method capable of shortening the tempo calculation time.

[0006]

In order to achieve the above object, according to the first aspect of the present invention, periodic sounds that occur periodically along the tempo of the music are continuously detected from the music from the sound source.
Based on the continuously detected periodic tones, two consecutive
Continuously determine the periodic sound time, which is one periodic sound interval time,
The number of periodic sound times close to the currently determined periodic sound time is calculated from M (M is a natural number of 2 or more) periodic sound times obtained in the past, and the calculated number is N (N Is a natural number smaller than M) or more, the average periodic sound time is calculated from the current periodic sound time and the past periodic sound time close to the current calculated periodic sound time, and the tempo is calculated from the calculated average periodic sound time. I do.

In this manner, two consecutive periodic sound times are successively obtained, and the periodic sound time which is closer to the presently obtained periodic sound time among the presently obtained periodic sound times and the M periodic sound times obtained in the past. Calculate tempo by calculating average period sound time from
That is, since the tempo is calculated without performing the matching process on a plurality of patterns, the tempo can be easily calculated, and thus the time for calculating the tempo can be shortened.

If there are a predetermined number of combinations of one of two consecutive periodic sound times that is three times the other of the M periodic sound times obtained in the past, the two periodic sound times The average time of the time is defined as the average periodic sound time. That is, among music, not only those in which periodic sounds are generated at fixed intervals, but also those in which one of two consecutive periodic sound times is three times as long as the other, the tempo of such music is also A plurality of patterns can be easily obtained without performing a matching process.

The periodic sound may be detected by detecting the rising of the level of the periodic sound.
In this case, the periodic sound is sampled, the periodic sound sampled this time is detected after a lapse of a predetermined time from the previous periodic sound detection, and the level of the periodic sound sampled this time is equal to or higher than the threshold and It is assumed that the rising of the level of the periodic sound is detected when the level of the periodic sound is larger than the level of the sampled predetermined number of periodic sounds.

[0010]

Embodiments of the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, an audio system (audio system) 10 includes a pair of speakers 12, a mini-disc recorder 14, a CD reproducing device 16, a cassette tape recorder 18, a tuner 20, an operation unit 24, and a display unit 30. The amplifier 22 is provided.

FIG. 2 shows a main control section of the audio apparatus according to the present embodiment. As shown in FIG. 2, the control system includes a sound source (for example, a mini-disc recorder 14, a CD,
Of the sounds from the playback device 16, the cassette tape recorder 18, and the tuner 20), sounds that periodically occur in accordance with the music tempo, for example, high frequencies (3 kHz to 15 kHz)
z) a spectrum analyzer IC 28 for detecting a sound (attack sound) having a predetermined frequency (for example, 3.4 kHz) and a sound (beat sound) having a predetermined frequency (for example, 105 Hz) on a low frequency side (100 Hz to 300 Hz). . The spectrum analyzer IC 28 is connected to a microcomputer (hereinafter, referred to as a microcomputer 26). The operation unit 24 and the display unit 30 are connected to the microcomputer 26.
Further, the microcomputer 26 is connected to an audio output IC 32 for selectively outputting a predetermined musical instrument sound or a plurality of rhythm patterns formed by combining a plurality of musical instrument sounds as shown in FIG. The audio output IC 32 and the sound source are the amplifier 22
It is connected to the. The microcomputer 26 is a sound source (14-20)
Control. As described above, since the microcomputer that controls the sound source controls the audio output IC, a plurality of functions can be shared and the device configuration can be simplified. That is, a dedicated rhythm microcomputer as in the conventional acoustic device is omitted.

Next, the operation of the present embodiment will be described.

In the present embodiment, as will be described later, a beat sound is detected from music from the sound source, the tempo of the music is calculated from the detected beat sound, and the time within one bar corresponding to the music tempo is calculated. Then, the audio output IC is controlled in one direction so as to output a rhythm pattern previously selected by the user. That is, the microcomputer 26 controls the sound output IC 3
Instructs to output a rhythm pattern regardless of the output state of 2. Therefore, the audio output IC 32 forcibly outputs the rhythm pattern. As described above, since the microcomputer controls the audio output IC in one direction, the processing can be simplified as compared with the case of bidirectional communication.

Thereafter, the audio output IC is connected to the microcomputer 26.
The rhythm pattern is repeatedly output within one measure of time corresponding to the tempo in accordance with the instruction from.

Here, the rhythm pattern is shown in FIGS.
As typically shown in FIG. 3D, each rhythm pattern is configured by combining a plurality of musical instruments with sounds. In each rhythm pattern, one bar time is, for example, the number of accents (16 in FIG. 3A, FIG. 3B), FIG.
The output timing of each musical instrument sound is set for each divided time divided by (D is 12). FIG. 3 shows typical rhythm patterns, and the rhythm patterns are not limited to these. Further, these rhythm patterns can be set by a user by providing a selection means.

On the other hand, the audio output IC repeatedly outputs a rhythm pattern within one bar corresponding to the tempo. However, the rhythm pattern to be repeatedly output may deviate from the music tempo. Then, a rhythm pattern synchronization process for synchronizing the rhythm pattern with the music tempo is executed.

Hereinafter, each of the above processes will be described in detail.

First, the process of detecting a beat will be described in detail with reference to FIG.

For example, reproduction of a certain music is started by a CD reproduction operation. At this time, the beat detection process shown in FIG. 4 is started by a predetermined switch operation.

At step 112 in FIG. 4, it is determined whether or not a low-frequency side sound (the above-mentioned beat sound) has been inputted. If a beat sound has been inputted, at step 114, a predetermined time has elapsed since the previous beat detection. It is determined whether or not the time U (for example, 187 msec) has elapsed. Here, the predetermined time U (187 ms)
ec) is a half of the time of one beat of a tune of 160 (160 beats per minute), which is a numerical value that is a little earlier than a general tempo.

If it is determined that the predetermined time U has elapsed since the previous detection of the beat sound, it is determined in step 116 whether or not the level of the currently input beat sound exceeds a threshold value. If none of the above three conditions are met,
Return to step 112. Therefore, as shown in FIG. 5, the sampling values SX, SY, and the like can be excluded. If the above condition 3 is satisfied, step 118
Then, the above three conditions (steps 112, 114, 11)
6) It is determined whether or not a variable C representing the number of input beat sounds satisfying 0 is 0. If the variable C is 0, step 11
At 0 and 120, the variable 1 is incremented, and step 1
At 24, the current sound level is stored in the area C, and the process returns to step 112.

On the other hand, if the variable is not 0, it means that a plurality of beat sounds satisfying the above three conditions have been input. In this case, in step 126, the current input level is determined based on the level stored in the area C. It is determined whether or not the level of the beat sound is larger by a certain amount. If it is not a certain amount,
The process returns to step 112 ignoring the beat sound input this time. On the other hand, if it is larger by a certain amount, in step 128,
It is determined whether the variable C is larger than C0 (for example, 4). If the variable C is equal to or smaller than C0, the variable C is incremented by 1 in step 130, and the area C is incremented in step 132.
And the process returns to step 112.
On the other hand, if it is determined that the variable C is larger than C0, there are C0 sounds that satisfy the above three conditions (steps 112, 114, and 116), that is, as shown in FIG. It can be determined that there was. That is, it can be determined that the rising of the beat sound has been detected. At step 134, the sound detected this time is set as a beat. At step 136, the data of each area C is reset, and at step 138, the variable C is initialized.

The beat detection processing is not limited to the above method, and the beat may be detected as follows. That is, the beat sound is sampled every predetermined time, and it is determined whether or not the predetermined time U has elapsed since the beat sound detected this time was detected as the previous beat. Hold the current sampling value. On the other hand, if the predetermined time U has elapsed from the time when the beat sound sampled this time is detected as the previous beat, a predetermined number of samples, for example, all four sampling values before the present sampling value are taken in, and It is determined whether or not the sampled value of is larger by a predetermined level than any of a predetermined number (for example, four) of past taken in values. The current sampling value is a predetermined number of past acquired (for example, 4
If the sampling value is not larger than all the sampling values by a predetermined level, the current sampling value is held. on the other hand,
If the current sampling value is larger than any of a predetermined number (for example, four) of the acquired past sampling values, it is set as a beat. In the above description, four sampling values are held. When a beat is detected, tempo calculation is executed based on the detected beat.

Next, the process of calculating the tempo will be described in detail with reference to FIG.

In step 142 of FIG. 6, a beat time is detected. That is, the time (beat time) from when the previous beat was detected to when the current beat was detected is detected. Note that, in the present embodiment, as shown in FIG. 7, the past eight beat times (B
T1 to BT8) are stored.

At step 144, the past M (for example, 8
The number of beat times (BT1 to BT8) is fetched, and in step 146, the number K of past beat times close to the current beat time (that is, substantially the same value) is detected. That is, the number K of beat times within ± 11 msec of the current beat time BT8 in the past M beat times BT1 to BT8.
Is detected.

At step 148, the number K is N (for example, 4
(Half), etc.). That is, it is determined whether the number of past beat times close to the current beat time is N or more.

If the number of past beat times close to the current beat time is N or more, an average beat time is calculated in step 150. That is, the average beat time of the current beat time and the past beat time close to the current beat time is calculated. If the number of past beat times close to the current beat time is less than N, the process proceeds to step 152.

By the way, the tempo of the music from the sound source is not always constant, and as shown in FIGS. 8A and 8B, a tune having a ratio of past beat times of 1: 3 or 3: 1 Since there is a tune of No. 1, it is determined in step 152. If the ratio of the past beat times is 1 to 3 or 3 to 1 in step 152, the time of one beat is reset as the average beat time in step 154. That is, (1.5 beat time +
(0.5 beat time) / 2.

In step 156, it is determined whether or not the current tempo has been calculated. That is, it is determined whether or not the number K of past beat times close to the current beat time is less than N.
If the tempo can be calculated this time, at step 158,
As shown in FIG. 9, a predetermined display portion 90H of the display unit 30
90L is turned on, and if the tempo could not be calculated this time, a predetermined display location 90
H, 90L flashes.

Here, the display section 30 illuminated in step 158 may be illuminated continuously during the performance of the same music piece from the point in time when the tempo is calculated. In step 160, the display unit 30 is made to blink, but it may be made to blink when the song ends because the tempo cannot be calculated for the performance of a certain song. In this way, the display unit 3
It is possible to prevent an operation in which 0 is repeatedly turned on and blinking.

In the next step 162, a tempo of 6
A value obtained by dividing 0 by the average beat time is calculated. Then, in step 164, the current beat time is stored in place of the previously stored beat time.

With the above processing, the tempo can be calculated. Then, one bar time T of the rhythm pattern described above is determined using the tempo calculated by this processing.
Therefore, one measure time of the rhythm pattern can be changed (closed) to the actual tempo of the music.

When calculating the tempo, if the number of past beat times near the current beat time is N or more, the average beat time between the current beat time and the past beat time near the current beat is calculated. Is calculated and the tempo is calculated, that is, the tempo is calculated without recognizing a fine pattern (corresponding to various rhythms or music genres), so that the tempo calculation time can be reduced.

The tempo calculation process is not limited to the above, and the tempo may be calculated as follows. That is, every time the M beat times are detected as described above, any of the M beat times, for example, the oldest beat time is compared with the other beat times, and the oldest beat time is compared. If there are N beat times near N, the average beat time may be calculated from the N beat times closest to the oldest beat time as described above, and the tempo may be calculated as described above.

The audio output IC repeatedly outputs a rhythm pattern after being instructed by the microcomputer, but the start of the rhythm pattern may be out of sync with the occurrence of a musical beat. FIG. 10 (A) shows a state of generation of a beat sound (sound on the low frequency side) which periodically occurs along with the tempo of the music, and FIG. 10 (B) shows an audio output IC.
Indicates that the rhythm pattern is output. In the example shown in FIGS. 10A and 10B, the first rhythm pattern P1 has a beat sound B at the start.
1 and is synchronized with the beat sound B2 at the start of the next one rhythm pattern P2, but the output timing of the beat sound B3 is not synchronized with the start of the next one rhythm pattern P3. In this way, if the start of the rhythm pattern and the occurrence of the beat of the music are shifted, the rhythm pattern sounds as if it does not match the music. Therefore, the rhythm pattern as the sound effect is unpleasant. Therefore, it is necessary to synchronize the start of the rhythm pattern with the beat sound. Therefore, in the present embodiment,
The rhythm pattern synchronization processing routine shown in FIG. 11 is executed.

In step 52 of FIG. 11, it has been determined whether or not a time Tt, which is a time obtained by subtracting a predetermined time (for example, 80 msec) t from one measure time T determined by the calculated tempo, from the time when the output of the rhythm pattern is started. Judge. If the time Tt has elapsed since the start of the output of the rhythm pattern, it is determined in step 54 whether or not one measure time T has elapsed since the start of the output of the rhythm pattern. If it is determined in step 54 that one bar time T has not elapsed since the start of outputting the rhythm pattern, step 5
At 6, it is determined whether or not a low-frequency side sound (beat sound) has been input. If a beat sound has been input, the processing after step 58 is executed, and if no beat sound has been input, the process returns to step 54. If it is determined in step 54 that one measure time T has elapsed since the start of the output of the rhythm pattern, in step 72, one measure time T is set to the predetermined time t.
It is determined whether or not the time T + t obtained by adding has elapsed. If it is determined in step 72 that the time T + t has not elapsed, it is determined in step 74 whether a low-frequency side sound (beat sound) has been input. If a beat sound has been input, the process from step 76 is executed. If no beat sound has been input, the process returns to step 72. As described above, steps 52, 54, 56, 72, and 74 monitor whether or not a beat sound has been input within ± a predetermined time t at the start of the rhythm pattern.

If it is determined in step 56 that a beat sound has been input, the next bar of the song starts before the output of one rhythm pattern is completed, that is, the time of the rhythm pattern is long (according to the calculated tempo). One measure time is long). That is, it can be determined that the calculated tempo is slow. In this case, a time ΔT (error (shift amount)) from when the beat sound is input in step 58 until one bar time T elapses is calculated.

It is determined whether or not the error ΔT is larger than a threshold value ΔT0. If the error ΔT is larger than the threshold value ΔT0, it means that the calculated tempo does not match (out of the allowable range), and the routine proceeds to step 66. On the other hand, when the error ΔT is equal to or smaller than the threshold value ΔT0, it can be determined that the tempo is correct (within the allowable range), and the process returns to step.

In step 66, an error distribution time is calculated. The error distribution time is a time obtained by dividing a time obtained by multiplying the error ΔT by a predetermined value, for example, twice, by a predetermined number of divisions (16 or 12) in the rhythm pattern. And step 68
Then, the error distribution time is allocated to each divided time of the rhythm pattern. That is, since the calculated tempo is slow, each divided time is shortened by the error distribution time.

Here, the error ΔT is multiplied by a predetermined value (for example, twice) as the error distribution time as follows. That is, if the error distribution time is simply obtained from the error ΔT and distributed as described above, the delay time is repeated due to a delay in the processing time of the microcomputer, and the tempo cannot be accurately set to an actual value. On the other hand, if the error .DELTA.T is multiplied by a predetermined value to determine the error distribution time and the distribution is performed as described above, the tempo can be accurately set to an actual value even if the processing time of the microcomputer is delayed. Therefore, the error ΔT is multiplied by a predetermined value (for example, twice) as the error distribution time. Incidentally, it was found from many experiments that doubling the error ΔT could accurately set the tempo to an actual value.

On the other hand, when a beat sound is input in step 74, as shown in FIG. 10, after the output of one rhythm pattern is completed (ie, after the start of the next rhythm pattern), the beat sound is detected. Can be determined. In other words, the time of the rhythm pattern is short (one measure time determined by the calculated tempo is short). That is, it can be determined that the calculated tempo is fast.

In this case, in step 76, the time ΔT from the lapse of one measure time T to the present time (when a beat sound is input)
(Error (shift amount)) is calculated.

In the next step 84, the above-mentioned distribution time is calculated, and in a step 86, the error distribution time is distributed to each accent interval of the rhythm pattern. That is, each accent time of the rhythm pattern is lengthened by the error distribution time.

Here, as described above, the tempo is calculated to determine the one bar time T. However, the present invention is not limited to this, and the one bar time T is corrected from the time ΔT. May be.

More specifically, the example shown in FIG. 10 will be described in more detail. For example, if the beat sound B3 is 30 msec later than the start of the rhythm pattern P3, it is determined that the rhythm pattern is faster, and the one rhythm pattern P3
Is delayed by 60 msec. In this case, if the rhythm pattern selected by the user is as shown in FIGS.
0 ÷ 16 = 3.75 msec is added to each accent interval. That is, it is added to the accent interval. In this embodiment, since the time is not counted for 1 msec or less, the remaining time is omitted.

According to the above-described method, a beat that appears almost regularly takes a predetermined time (for example, ± 80 msec).
Within the range, the rhythm pattern and the music can be synchronized.

Since the tempo values are 81 to 160, and it is possible to observe the tempo from a half of 81 to a tempo of 160, the minimum beat interval is assumed to be 187 msec. Therefore, the monitoring time is set to a fixed value of ± 80 msec.

By the above processing, a beat sound is detected from the music signal as shown in FIG. 12A as shown in FIG. 12A, and one rhythm pattern is drawn according to the tempo calculated from the beat sound. 12 (C) and output as shown in FIG. 12 (D). As shown in FIG. 12 (C), even when the synchronization is performed at the first start or when the start of the next rhythm pattern deviates from the beat sound, the start of the rhythm pattern is performed as described above. A predetermined time (± 80 msec) before and after the time is monitored, and an error between the start of the rhythm pattern and the time of detection of the beat sound is canceled out in the rhythm pattern, so that synchronization can be achieved.

By the way, as shown in FIG. 12D, the start timing of the rhythm pattern may be shifted even if one measure time of the rhythm pattern matches one measure time of the music. In this case, the beat near the moment when the tempo was calculated and the start time of the rhythm pattern are started in synchronization with each other so as to be within ± 80 msec.

Next, with reference to FIG. 13, a description will be given of a sound effect adding process routine that is started by a predetermined operation of the operation unit.

In step 92 of FIG. 13, the low frequency side (100
Hz to 300 Hz) (for example, 105H
It is determined whether or not the first sound (beat sound) of z) is input. If the beat sound has not been input, it is determined in step 94 whether or not the second sound (attack sound) of the second frequency (for example, 3.4 kHz) in the high frequency side (3 kHz to 15 kHz) has been input. to decide. If no attack sound has been input, the process returns to step 92.

If it is determined that a beat sound has been input, the sound output IC 32 is controlled in step 96 to output a first sound effect determined corresponding to the beat sound. The display location 90L determined corresponding to the first sound (beat sound) is made to blink, and step 94 is performed.
Proceed to.

On the other hand, when an attack sound is input,
In step 100, the audio output IC 32 is controlled so as to output the second sound effect determined corresponding to the attack sound, and in step 102, the display location 90H determined corresponding to the attack sound is caused to blink. Go to step 92.

As described above, every time a beat sound or an attack sound is detected, a sound effect determined corresponding to these sounds is output, and a display portion defined corresponding to these sounds blinks. The effect can be generated visually. Also, the tempo can be taken visually.

In the above, the tempo is calculated using the beat sound and the start time of the rhythm pattern is synchronized. However, the present invention is not limited to this. The tempo is calculated using the attack sound. The start time of the rhythm pattern may be calculated and the start time of the rhythm pattern may be synchronized.Furthermore, not only the beat sound but also the attack sound may be used to calculate the tempo or synchronize the start time of the rhythm pattern to use the beat sound. If it is not possible to calculate the tempo or synchronize the start time of the rhythm pattern, the attack sound may be used to calculate the tempo or synchronize the start time of the rhythm pattern.

[0058]

As described above, according to the present invention, two consecutive periodic sound times are successively obtained, and the presently determined period between the presently obtained periodic sound time and the M periodic sound times obtained in the past is obtained. The average tempo time is calculated from the periodic sound time close to the sound time, and the tempo is calculated. That is, since the tempo is calculated without performing the matching process on a plurality of patterns, the tempo can be easily calculated. This has the effect that the time for calculating the tempo can be shortened.

[Brief description of the drawings]

FIG. 1 is an external view of an acoustic device according to an embodiment.

FIG. 2 is a block diagram showing a main control system of the audio device according to the present embodiment.

FIG. 3 is a diagram showing a table of a plurality of rhythm patterns.

FIG. 4 is a flowchart showing a beat detection processing routine.

FIG. 5 is a diagram showing how a beat is detected.

FIG. 6 is a flowchart showing a tempo calculation processing routine.

FIG. 7 is a diagram showing the timing of generating beat sounds of a music piece having a constant tempo.

FIG. 8 is a diagram showing how beats of a tune having a tempo of 1 to 3 or 3 to 1 are generated.

FIG. 9 is a detailed view of a display unit.

FIG. 10 is a timing chart of a beat sound and a rhythm pattern.

FIG. 11 is a flowchart showing a rhythm pattern synchronization processing routine.

FIG. 12 is a timing chart showing a difference between a beat sound and a rhythm pattern.

FIG. 13 is a diagram showing a sound effect adding process routine.

FIG. 14 is a block diagram showing a part of a control system of a conventional acoustic device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Audio system 12 Speaker 14 Mini disk recorder 16 CD reproduction device 18 Cassette tape recorder 20 Tuner 22 Amplifier 24 Operation part 26 Microcomputer 28 Spectrum analyzer IC 30 Display part 32 Audio output IC

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H04R 3/00 310 H04R 3/00 310

Claims (4)

[Claims] 1. A method for detecting, from music from a sound source, periodic tones periodically generated along the tempo of the music, and detecting two consecutive tones based on the continuously detected periodic tones.
The periodic sound time, which is one periodic sound interval time, is continuously obtained, and the number of periodic sound times close to the periodic sound time obtained this time is determined from M (M is a natural number of 2 or more) periodic sound times obtained in the past. If the calculated number is equal to or greater than N (N is a natural number smaller than M) out of the M, an average is calculated from the currently obtained periodic sound time and the past periodic sound time close to the currently obtained periodic sound time. A tempo calculation method that calculates the periodic sound time and calculates the tempo from the calculated average periodic sound time. 2. When there are a predetermined number of combinations in which one of two consecutive periodic sound times is three times the other of the M periodic sound times determined in the past, the two periodic sounds The tempo calculation method according to claim 1, wherein an average time of time is set as the average period sound time. 3. The tempo calculation method according to claim 1, wherein the periodic sound is detected by detecting a rise of the level of the periodic sound. 4. The method according to claim 1, wherein the periodic sound is sampled, a periodic sound sampled this time is detected after a lapse of a predetermined time from the previous periodic sound detection, and a level of the periodic sound sampled this time is equal to or more than a threshold value. 4. The tempo calculation method according to claim 3, wherein a rising of the level of the periodic sound is detected when the level of the periodic sound is higher than a predetermined number of periodic sounds sampled in the past.