JPS61138995A - 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 a musical tone generator used in an electronic musical instrument or the like, or to an L81 version of the musical tone generator to improve the tone color changing function.

[Conventional technology]

Low-pass digital signal processing in a closed loop
For example, the method of creating a gradually changing sound by inputting an initial waveform with a filter or an all-pass filter into a loop is as follows: Karplus,
L et al.”Digital 5ynthesis of Pl
uckea String ana Drum Tim
bers"Computer Music Journa
l vol, 7. /h2, etc.

[Problem that the invention seeks to solve]

However, although the method described in the above literature can successfully generate routine sounds, it seems to be lacking in some cases, such as when you want musical sounds like sound effects or when you want to add varying sounds to musical sounds.

Therefore, in order to solve these drawbacks, this invention
Musical sound generator I that can give irregular changes to musical sounds and generate interesting musical sounds both as sound effects and as normal musical sounds! The overall objective is to obtain an electronic musical instrument having the following characteristics.

[Means for solving the problem] In order to solve the above problem, - The multiplier of the multiplier used in the all-pass filter included in the patrol loop is fluctuated with an irregular signal, and the I added a change to the musical tone played.

[Operation] Figure 3 shows the phase (delay) characteristics of the all-pass filter. The vertical axis is the phase lag divided by the sampling period. This is the multiplier given to the value C in the figure to the multiplier of the all-pass filter.

When the value of this multiplier C is fluctuated by an irregular signal, the phase characteristics of the all-pass filter change, which in turn changes the fundamental frequency and overtone composition ratio of the musical tone, resulting in a musical tone that changes in a complex manner.

[Example] The second prisoner has 40.2 all-pass filters and 50.6 Off filters in the roof, and 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 fist filter 4.
0. In the unlikely event that a filter operation is performed using a Lupass filter 50.60, RAM (Ran-dom Access M
20 is a circuit block diagram of a musical tone generation circuit of the type storing in memory) 20. FIG.

The low-pass filter 40 is provided in response to the fact that the sound of natural musical instruments gradually attenuates from the high frequency range over time.

After going through the loop many times, the low-pass filter 4
The high range is attenuated due to the effect of 0. The speed of attenuation is changed by the multiplier applied to the multiplier in the low-pass filter. That is, by changing the multiplier t-', the frequency characteristics of the low-pass filter 40 change.

The all-pass filter 50.60 has a phase delay characteristic as shown in FIG. 115 (7). FIG. 3 shows, by the value of the multiplier CI, (!2) of the multiplier of the all-pass filter 50, 60, how many sampling periods are obtained when the signal is passed through this all-pass filter.

Moreover, as the values of al and c2 become closer to -1, the phase characteristics become more undulating.

In addition, 01. When c2 is fixed near -1, does the delay characteristic vary depending on the frequency included in the musical tone? It shows. In other words, setting it near al, c2t--1 means that non-integer harmonics are generated. Non-integer harmonics are an extremely important factor in creating natural musical sounds and effective synthetic sounds.

In particular, non-integer overtones are an essential factor when creating piano sounds or bell tt-tones.

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

Next, I will explain the principle of creating an accurate complete scale using this method.

The filtered data is written to RAM20. Once the waveform in the initial waveform ROM 10 has been read out for one cycle, it will not be used again, and the data circulating within the loop will be stored in the RAM.
20.

These controls are performed by the switching circuit 30.

The time from when data is written to this R, AM 20 until the next data is read is tx, and the delay time at low-pass filter 40 is t-tt, pp + all-pass filter 50.60. Each delay time is 1:
APFl + tAPF! Then, the natural frequency in the loose, ie, the fundamental frequency fo of the generated musical tone, is as follows.゛If the denominator and numerator of the above equation are multiplied by the sampling frequency 78', then, N = tzX fe α = tLpyX713 β = tAPyIX fa γ = t APyt X f B .

Here, α and β are uniquely determined in order to create a desired musical tone. N can only be 1, which is an integral multiple of the sampling period.

Therefore, the scale of the generated musical tone is roughly adjusted by the time of writing to and reading from the RAM 20, and finely adjusted by γ, that is, the multiplier c2 of the multiplier 62 included in the all-pass filter 60.

Next, giving this multiplier c2Vc fluctuation in total will be explained. FIG. 1 is a circuit diagram for providing an irregular fluctuation amount to the multiplier 02.

In Fig. 1, 1 is a noise generation circuit that generates irregular signals, and is connected to a 15-stage shift register and an exclusive OR (l).
It consists of an X-0R) gate. The repetition period of this noise generation circuit 1 is 52767 times, so if the sampling frequency fB == 40 KHz, the repetition period is 52767 times.
The return cycle is approximately 18 seconds. If a longer repetition period is required, the number of stages of the shift register can be increased.

The output of the noise generation circuit 1 is sent to the adder 3 via the selection circuit 2.
connected to.

The selection circuit 2 is a circuit that selects which bits of the output of the noise generation circuit 1 are to be transferred to the next adder 5, and the number of bits to be transferred is determined by the control signal 2a. Of course, as the number of bits to be transferred increases, the fluctuation liability of the multiplier 02 also increases.

The adder 3 adds the 02 value for fine-tuning an accurate musical scale and the value selected from the noise generating circuit 1, and is connected to the all-pass filter 60 as a multiplier 620.

When the multiplier C2 changes, the phase delay of the all-pass filter 6υ changes, as shown in the phase characteristics of FIG.
As a result, as can be seen from equation (2), the fundamental frequency of the musical tone changes. Furthermore, depending on the noise, the phase characteristics may have undulations, so that non-integer harmonics may occur.

Although only 8 bits of the output of the noise generating circuit 1 are used in FIG. 2, it is of course possible to use more bits.

Furthermore, if the selection circuit 20 control signal 2at is changed over time, the multiplier C2 has a fluctuation that changes over time.
You can create more interesting musical sounds.

〔Effect of the invention〕

As described above, by using the present invention, it is possible to create musical tones that change in a very complex manner with the addition of a simple circuit, so it is possible to provide an electronic musical instrument suitable for simulating natural musical instruments and creating sound effects.

[Brief explanation of the drawing]

FIG. 1 is a circuit for giving a fluctuation amount to the multiplier of an all-pass filter showing an embodiment of the present invention, FIG. 2 is a block diagram showing a tone generation system, and FIG. 3 is a phase characteristic diagram of the all-pass filter. 1... Noise generation circuit 2... Selection circuit 6... Adder 10... Initial waveform ROM 20... RAM 50... ...switching circuit

Claims (1)

[Claims] It includes at least a low-pass filter and an all-pass filter for digital signal processing in a loop, writes the output of the final stage of the filter to a semiconductor memory, and reads data stored in the semiconductor memory at a predetermined timing. , in a musical tone generating device of a type that forms a musical tone by writing into the semiconductor memory again after performing a filter operation, means for applying a multiplier to a multiplier used in the all-pass filter is a noise generating circuit. An electronic musical instrument having a musical tone generating device, characterized in that it is equipped with an adder and an adder.