JPS61138994A - Electronic musical instrument - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an improvement in the vibrato function of a musical tone generating device used in an electronic musical instrument or the like, or a musical tone generating device FLLF:L8 engineered version.

(Prior Art) A method of creating a gradually changing musical tone by using a low-pass filter and an all-pass filter that perform digital signal processing in a closed loop and inputting an initial waveform to the loop is, for example, Karplus. ,
%Digxtal 19ynthegis of
Pluck@4 String and Drum
Tlmbers '%computer Mus
It has been reported in ic JOurQal Vol. 7, Mu 2, etc.

However, in order to apply vibrato to a musical tone using the method described in the above document, digital data must be converted into an analog signal! 7 LFO (LovrFre
The only way to do this is to apply an analog biprato using an analog device, but this requires a peripheral circuit, and there is a risk that the meaning of digitally producing musical tones will be diluted.

Therefore, in the present invention, a musical tone generating device, or a musical tone generating LSI, which processes digitally without increasing the number of special analog circuits, and has a simple and highly effective vibrato circuit that does not require a multiplier. The purpose is to provide an electronic musical instrument with

[The tth method to solve all problems]

In order to solve the above problem, the multiplier of the multiplier used in the all-pass filter included in the loop was set to (1
A vibrato effect is obtained by setting the first circuit.

[Effect]

The element 4 in FIG. 1 is based on the following equation.

Spider + torture (x + y) = 2 + 2my stn (x + y/2
) -(D, that is, the sine waveform value is stored and 7'(R
OMRead 0nly Memory ) f<, the sum of the output value when accessing with I and the output value when accessing with (x + y) is +2. −
Since the result is a sine wave of 2, this sum is biased with a maximum width of ±1, and is used as the multiplier of the multiplier described above. The phase characteristics of the all-pass filter change by changing the value of the multiplier. Since the four frequencies of the musical tones formed by the loop are changed in a sine wave manner, a vibrato effect can be obtained.

〔Example〕

FIG. 2 shows a low-pass filter 40.2 all-pass filters 50.60f in the loop, 1. , an initial waveform ROM that stores one cycle of the initial waveform of the musical tone to be generated.
A waveform signal is read out from the low-pass filter 4.
0, All Pass Fist Filter 5 Jr, 6. After performing the filter operation with g' and t, the RAM (Ran4om kcc8ss
This is one side of a circuit block of a musical tone generation circuit which is stored in Memory ) 20.

The low pass filter 40 is designed to accommodate the fact that the sound of natural instruments gradually attenuates from the higher frequencies over time.

After going through the loop many times, the low-pass filter 4
Due to the effect of 0, high frequencies are attenuated. The speed of attenuation can be changed by the multiplier applied to the multiplier in the low-pass filter7.
This is the point at which the frequency characteristics of the filter 40 change.

The all-pass filter 50.60 has a phase (delay) as shown in FIG. 3: f! f+! 11. The vertical axis in FIG. 5 is the delay time of the filter divided by the sampling period. In other words, the multiplier's multiplier, CI, and C2 indicate how many sampling periods are delayed when the signal is passed through the all-pass filter.

Moreover, as the values of CI and C2 become closer to -1, the curve becomes thicker.

This shows that when CI and C2 are fixed near -1, the four-note characteristics differ depending on the frequencies included in the musical tone.In other words, when CI and C2 are set near -1, the non-row frequency It means to generate overtones. natural musical tone,
, non-integer harmonics are an extremely important factor in creating effective synthesized sounds. In particular, non-integer harmonics are essential when creating piano sounds or bell sounds.

All-pass filter 50 thus serves to generate non-integer harmonics.

Next, the principle of creating accurate musical scales using this method will be explained.The filtered data is written to the RAM 20. Once the initial waveform ROM 100 waveform Iζ is read out for one cycle, it will not be used from the next time, and the data circulating in the loop will be
It is read out from RAM20.

These controls are carried out by a switching circuit 60 - this R
The time from when data is loaded into the AM20 until the next time it is read out is t, x, the delay time in the low-pass filter 40 is thPF, and the delay time in the all-pass filter 50.60 is respectively t AFF l,
If t AP1P2, this becomes the natural frequency within the loop, that is, the fundamental frequency f0 of the generated musical tone.

When the denominator and numerator of the above equation are multiplied by the sampling frequency fB'f:, then, N=txXf8 α=iLPyxfs β=t)IQ! I X f 5 r=tAPF, x fs .

Here, α9. θ is uniquely determined to produce the desired wheezing sound. N can only be a value that is an integral multiple of the sampling period.

Therefore, the scale of the generated musical tone is roughly adjusted by the time it takes to load and output the data into the RAM 20, and then finely tuned by the multiplier C2 of the multiplier 62 included in the r, sunawachi, and all-pass filter 60. become.

Next, we will show how to apply vibrato to the sound using this tone generation method.

By changing the multiplier 620 multiplier C2 in the all-bass filter 60, the fundamental frequency of the musical tone changes.
This is possible if this Czk is varied in time. However, if a multiplier or the like is used to change C2 over time, the circuit becomes enormous, and the musical tone generator is built on a one-chip LSI.
It will no longer be possible to configure it.

FIG. 41 shows a vibrato circuit that does not use a multiplier, which is the gist of the present invention. In FIG. 1, 105° 104 is an fr-ROM table that stores the values of the sine waveform. R.O.
The M table 105 is accessed by the address t generated by the address generation port @100. ROM table 104
is accessed by adding the output y of the clock generation circuit 101, the output of the address generation circuit 100, and I in the adder 102 and using the resultant value (x+y).

The outputs of the accessed constant ROM tables 103 and 104 are added by an adder 105.

The output of the adder 105 corresponds to equation (2).

That is, it becomes a sine wave whose amplitude is controlled by Y.

As is clear from equation (2), the output of this adder 105 is shifted to the right by the next shift circuit 106 with a maximum width of ±2.
The bits are shifted and the value is sacrificed. (This is -1≦C
2≦1) The output of the shift circuit 106 is added to the bias values C and B in an adder 107, and after t, the output of the shift circuit 106 is added to the bias values C and B. It is given as a multiplier of '1Ei62 to the power of bus filter 60.

A bias is applied to the bias straight line 11Bll''tC2 so that the vibrato frequency can be captured as vertically symmetrically as possible.

As can be seen from this explanation, the output I of the address generation circuit 10G at j'5 corresponds to the vibrato frequency, and the output I of the address generation circuit 10G corresponds to the vibrato frequency.
The output y of 1 is the depth of the vibrato (targeted. If the output The vibrato frequency will increase if you read the address in large numbers.

Further, when the output y of the clock generation circuit 101 is fixed at a certain f, it becomes a sine wave waiting for the width value of the equation (2), and changes into a C, ij sine wave. Therefore, the depth of the vibrato can be controlled by Y. If y is changed over time, the depth of the vibrato changes over time, so it can also be used as a delay vibrato.

Furthermore, the present invention can be applied to cases where the fundamental frequency of a musical tone is changed by the first minute of musical tone generation.

Note that in FIG. 1, V; 9 has two R and 'OM tables for convenience of explanation, but it goes without saying that using one ROM table in a time-sharing manner simplifies the circuit.

〔Effect of the invention〕

As stated above, by using the present research, it is possible to easily construct a vibrato circuit without using the power of 4, and it is also possible to add not only vibrato functions but also individual changes to musical tones.

[Brief explanation of drawings]

Figure 1 shows the vibrato circuit showing Akira Motoyaku's mango row,
The figure is a block diagram showing a musical tone generation system, and Figure 3 is a phase characteristic diagram of an all-pass filter.10...Initial waveform ROM 20...RAM 30...Switching Circuit 40...Low pass filter 50.60...All bus filter 70...
...Mixer 62...Multiply '44 100...Address source main circuit 101...Redirect a to main circuit 102.1 (15, IO2... ...Adder 103.
104...ROM table 106...Shift circuit 110...- Switching! more than the passable distance

Claims (2)

[Claims] (1) At least a low-pass filter and an all-pass filter for digital signal processing are provided in the loop,
The output of the final stage of the filter is written to the semiconductor memory, and the data stored in the semiconductor memory is read out at a predetermined timing, and after filtering is performed, the data is written to the semiconductor memory again. An electronic musical instrument having a musical tone generating device of a type that generates a musical tone, characterized in that the musical tone generating device includes a circuit that temporally changes a multiplier given to a multiplier used in the all-pass filter. (2) The circuit for changing the multiplier over time is characterized in that the circuit comprises at least a semiconductor memory storing a sine waveform value, an adder, and an address generation circuit for accessing the semiconductor memory. An electronic musical instrument according to claim 1.