JPS61255398A - 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] (Industrial Application Field) The present invention relates to electronic musical instruments, and in particular to reduction of quantization noise in musical tone generators that generate musical tones by digitally multiplying waveform data and envelope values. It is related.

(Prior Art) In recent years, electronic musical instruments have become capable of creating sophisticated sounds with the introduction of digital signal processing technology. An example of such an electronic musical instrument is disclosed in Japanese Patent Laid-Open No. 59-214091.

A block diagram of this conventional example is shown in FIG. 4, and its functions will be outlined below.

Performance information from the performance operation of the electronic musical instrument is sent to the musical tone generator 1 through the microcompass, and the musical tone generator 1 reads predetermined waveform data W from the ROM 2 in response to tone designation data etc. in the performance information. . Further, the musical sound generating section 1 generates an envelope E, which is a time-varying characteristic of volume, based on the performance information, and multiplies it with waveform data W to generate a musical sound signal WE.

Furthermore, the musical tone generator generates a note clock corresponding to the pitch data in the performance information, and outputs the D/A converted musical tone signal WE at the note clock period.

The output musical tone signal wE having an analog value has aliasing noise caused by the note clock removed by a filter 3, and is then sounded by a speaker 4.

The core of the musical tone generator that generates the musical tone signal WH can be expressed simply as shown in FIG. 5, as shown in FIG. wE' is the number of bits of the DA converter 6 (N
), it is not possible to DA convert all the bit numbers of the true value WH of the multiplication result, and the upper N bits of vE are used as valid data. Normal waveform data is 1
2 to 16 bits, envelope 10 to 16 bits, D
The number of bits of the A converter is currently 16 bits at most, and a truncation error always occurs.

(Problems to be Solved by the Invention) When the number of bits of the waveform data W is a and the number of bits of the envelope E is b, the number of bits of the WXE multiplication result is a+b. Normally, when the number of bits N of the DA converter performed after this operation is N < a + b.

In the operation result, the upper N bits of the bit number a+b are treated as valid data, and the parts less than valid data are discarded.

In other words, the calculation result of the WXE multiplication, which should be E, is treated as w-E', which includes a truncation error.

The waveform data W is a repeating waveform of a waveform that amplitudes symmetrically in positive and negative directions around zero, and the envelope E is an attenuated envelope that gradually attenuates and finally becomes zero.

Fig. 6 shows the relationship between the waveform data W, the envelope E, and the true value VE of the musical tone signal which is the result of multiplication of both, and Fig. 7 shows the true value WE of the musical tone signal and the effective data WE after truncating.
Figure 8 shows the relationship between wE when the envelope is large.
' is shown by a solid line, WE' when the attenuation has progressed is shown by a broken line, and FIG. 9 shows IIE' when the attenuation has further progressed.

In other words, as shown in FIG. 7, the true value WE of WXE and the valid data WE' have a relationship of O=I wE I-I ME' K:1, assuming that the LSB of the valid bit is 1.

As the attenuation progresses further, as shown by the broken line in Figure 8, WE' takes on values of O and +1 in the region where the waveform data is positive, and values of -1 and -2 in the region where the waveform data is negative. will be taken.

As the attenuation progresses further, as shown in Figure 9, wE''=0 in the region where the waveform data is positive, and WE'=0 in the region where the waveform data is negative.
-1.

When the attenuation further progresses, it becomes VE'lIO.

As explained above, in the conventional method, the waveform data W
Even though the center value of the amplitude of is zero, the musical tone signal W
There was a problem in that the center value of the amplitude of E' was 0.5, which resulted in deterioration of sound quality.

There is another major problem with the conventional methods. As mentioned earlier, as the envelope attenuates, the musical tone signal wE' attenuates with the center value of the amplitude at -0.5 as shown in FIG.
As shown in the figure, vE' suddenly changes to duty 50 between 0 and -1.
% square wave. The rectangular wave is a very noisy sound and has a large duty, so the volume suddenly increases to the auditory sense.

This state continues until it matches the envelope E, no matter how much the envelope E attenuates and approaches zero.

This follows from the decay of the envelope E.

The volume of the musical tone was gradually decreasing, but at a certain point the volume suddenly increases, and the volume remains constant while changing to a noisy, foreign sound. When the envelope E reaches zero, it suddenly makes a "pop" sound. means disappearing.

This is different from the natural attenuation of sound volume and is extremely inconvenient.

As described above, the conventional example has two problems: the S/N ratio is poor and the dynamic range is unnatural.

SUMMARY OF THE INVENTION In view of the above problems, the present invention provides an electronic musical instrument with improved sound quality distortion caused by truncation errors during multiplication.

(Means for Solving the Problems) In order to solve the above problems, the electronic musical instrument of the present invention has the following features:
This has a configuration that includes means for adding 1 to one bit below B.

(Function) With the above-described configuration, the present invention can reduce the distortion of the tone quality by +0.5, which has been caused by the center value of the amplitude of the musical tone being -0.5 due to the truncation error of multiplication. This is improved by setting the center value of the amplitude to zero.

(Example) An embodiment of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of an electronic musical instrument using a musical tone generator according to the present invention. To explain this FIG. 1, 1-1 is a keyboard. 1-2 is a tablet.

This is an operation section that instructs selection of the tone color of the musical tone output from this electronic musical instrument. Reference numeral 1-3 denotes an effect switch, which controls various effects on musical tones, such as turning on/off effects such as vibrato and tremolo. 1
-4 is a microcomputer, such as Intel's microcomputer 8049. 1-5
1-6 is a musical tone generating section, which performs waveform calculation and frequency calculation based on the control signal given by the microcomputer 4. 1-6 is a data bank, which stores the waveform data envelope data used in the musical tone generating section 1-5. The stored ROM (
read-only memory). A filter 1-7 removes aliasing noise from the musical tone signal output from the musical tone generating section 1-5. 1-8 is a speaker.

Next, the operation of the electronic musical instrument shown in FIG. 1 will be explained.

The microcomputer 1-4 operates the keyboard 1-1, tablet 1-2, . Effect switch 1-3
The state of construction will be gradually completed horizontally. Also, the microcomputer 1-4 is the keyboard 1-
Based on the 0N10FF state of the key in tablet 1-2. Control data is sent out depending on the state of the effect switch 1-3. In the musical tone generating section 1-5, the assignment signal and other control signals sent from the microcomputer 1-4 are taken into internal registers, and based on these signals, necessary waveform data and envelope data are generated from the data bank 1-6. The musical tone signals synthesized in the musical tone generating section 1-5 are sent to the speaker 1-8 through a filter 1-7 to generate musical tones.

The envelope data 1, for example, is a differential display of the slope of the envelope, and by sequentially adding the data, an envelope that changes every moment can be created.

For example, the waveform data is read out repeatedly by sequentially reading one period of waveform data stored in data banks 1 to 6, and once reading of one period of data is completed, reading one period of data again. .

The arithmetic unit of the present invention is shown in FIG. This figure shows a case where the number of bits of the waveform data W is 12 bits, the number of bits of the envelope E is 10 bits, and the number of bits of the DA converter is 12 bits.

The multiplier 11 performs WXE and outputs 22-bit vE, but since the number of bits of the DA converter 13 is 12 bits, the necessary bits of WH are 12 bits. That is 22
The upper 12 bits of bit IIB become the required number of bits, and the 1 multiplier 11 adds one more bit to the lower order, and
Outputs 3 bits vE'. The adder 12 adds 1 to the 13-bit vE' to create a 13-bit addition result, but ignores the LSB and outputs the upper 12 bits of data as a digital musical tone signal 11E''.The 12-bit D
The A converter 13 performs DA conversion on the 12-bit WE'' and outputs it as an analog tone signal WE''.

FIG. 3 shows the true value WE of the musical tone signal and the musical tone signal WE'' of an embodiment of the present invention.Furthermore, WE'' when the envelope E becomes small is shown by a broken line in FIG.

That is, the center value of the amplitude of the musical tone signal of the present invention becomes zero, and the distortion in tone quality as described in the conventional example can be eliminated.

Furthermore, another problem, that is, when the envelope becomes sufficiently small, the decaying musical tone suddenly changes to a foreign sound and becomes louder, does not occur.

In other words, according to the present invention, as the envelope attenuates, the amplitude and duty of the musical tone decrease moment by moment, with the center value of the amplitude set at zero, as shown in FIG. In other words, the volume gradually decreases and approaches zero.

In other words, both the S/N ratio and dynamic range, which were two major problems in the past, have been dramatically improved.

(Effects of the Invention) As described above, the present invention makes it possible to set the center value of the amplitude of a musical tone signal to zero by adding +1 to one bit below the LSB of the required number of bits of the result of multiplying waveform data and an envelope. This eliminates the distortion in sound quality and the unnaturalness when the volume attenuates.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a waveform data and envelope multiplication section of the musical tone generating section of FIG. 1, and FIG. 3 is an explanatory diagram of a musical tone signal of the present invention. Figure 4 is a block diagram of the conventional example, Figure 5 is the waveform data and envelope multiplier in the conventional example, and Figures 6 to 9.
The figure is an explanatory diagram of a conventional calculation. ■-5...Musical tone generator, 11...Multiplier, 12...
-Adder, 13...DA converter. Patent Applicant: Matsushita Electric Industrial Co., Ltd. Figure 1 Figure 2 Figure 1 ■ Figure 3 Figure 4 Figure 5:) Figure 6
Figure 7 Figure 8 Figure ◆ 8 Figure 9

Claims (1)

[Claims] An electronic musical instrument that generates a musical tone signal by multiplying waveform data and an envelope, characterized in that 1 is added to one bit below the LSB of the required number of bits of the result of multiplying the waveform data and the envelope.