JP2625670B2 - Musical sound wave generator - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a musical sound generator that generates a musical tone waveform using a digital circuit to generate musical sounds, such as an electronic musical instrument.

[Conventional technology]

In a conventional analog music synthesizer, it has been practiced to use a VCF to realize a resonance effect that causes a peak in amplitude characteristics near a cutoff frequency. In order to perform such a resonance effect using a digital circuit, (a) in the case of sine wave addition synthesis, the coefficient (high frequency coefficient) of a specific harmonic is increased, and a peak is generated in the harmonic amplitude value (harmonic content). There is a method of realizing the same function as an analog filter by using a digital filter (for example, a digital low-pass filter).

[Problems to be solved by the invention]

According to the above prior art, according to (a), in order to generate a satisfactory harmonic, a large number of calculation channels are required, and the amplitude level must be variably set for each harmonic. According to (b), there is a problem that the digital filter itself has a large circuit scale and is difficult to realize.

〔Purpose〕

By the way, the present applicant has previously made one proposal for solving such a conventional technique (Japanese Patent Application No. 57-225582, "Method of Generating Musical Sounds of Electronic Musical Instruments"). In connection with the proposal, an object of the present invention is to provide a waveform generation method of an electronic musical instrument capable of obtaining a more varied resonance effect.

[Means for solving the problem]

In other words, the present invention takes the maximum level from the address signal for reading the waveform for a predetermined period in one cycle of the address signal, and from the maximum level to the minimum level or from the minimum level to the maximum level in other periods. There is a tone waveform generator which generates a changing envelope signal and multiplies the envelope signal by a plurality of waveform signals generated in one cycle of the address signal to generate an output waveform signal.

〔Example〕

Hereinafter, the present invention will be described in detail with reference to an embodiment shown in the drawings.

FIG. 1 shows a block circuit according to the present embodiment.
Is a keyboard, and signals corresponding to operation of a plurality of keys provided on the keyboard 1 are transmitted to the frequency information generating circuit 2. The frequency information generation circuit 2 outputs frequency information corresponding to the operation key and supplies the frequency information to the phase angle calculation circuit 3.

The phase angle calculation circuit 3 accumulates the supplied frequency information at each predetermined timing to generate a signal indicating a phase of a waveform that changes sequentially, that is, an address signal, and supplies the generated signal to the N input terminal of the waveform generation circuit 4.

The modulation signal generating circuit 5 generates a modulation signal from the keyboard 1 for sequentially changing the shape of the output musical tone waveform in accordance with the operation of the key to change the content of the harmonic component.

The modulation signal is applied to an addition circuit 6 and added together with a manual input modulation signal whose content changes due to a player's volume operation or the like.
Applied to input.

The waveform generation circuit 4 corrects an address having a cycle longer than one cycle of the waveform while the address signal specifies one cycle of the waveform from the address signal supplied from the N input terminal and the modulation signal provided from the M input terminal. Get address signal,
With this modified address signal, the waveform information is read from the memory, and the read waveform information takes the maximum level for a predetermined period in one cycle of the address signal and changes from the maximum level to the minimum level in other periods as described later. , And a resulting waveform signal is output from the zero output terminal.

Then, the output waveform signal from the 0 output terminal is supplied to an envelope multiplying circuit 8 together with an envelope control signal output from an envelope control signal generating circuit 7, and after being envelope-multiplied, sent to a digital / analog converter (DAC). Thus, an analog waveform signal is obtained.

The envelope control signal generating circuit 7 is supplied with a signal indicating a key operation from the keyboard 1, and generates an envelope control signal having a predetermined shape.

Figure 2 shows a detailed circuit configuration of the waveform generating circuit 4 of FIG. 1, the modulation signal M ₀ ~M ₁₁ input from M input end, the B input terminal of the multiplier circuit 41 (B ₀ ~B ₁₁₎ Applied. Also, N
Address signal N ₀ to N ₁₁ which is input from the input end, the multiplication circuit 4
1 are applied to the A input terminals (A _{0 to} A ₁₁ ).

Then, the multiplication circuit 41 outputs a result of multiplication, that is, a value obtained by multiplying the signal (referred to as A) from the A input terminal and the signal (referred to as B) from the B input terminal by 2 ⁻¹² , that is, A × B ÷ 2 The value of ¹² is output.

Then, the calculation result of the lower 8 bits (Q ₀ ~Q ₇₎ output is applied to the waveform memory 42. Incidentally, the upper side output of the multiplier circuit 41 (Q ₈ ~Q ₁₁₎ is not used. The waveform memory 42 stores a cosine wave for one cycle. That is, to become A input end (A ₀ to A ₇₎ in given signal is an address signal of the waveform memory 42 (i.e., correction address signal obtained by modifying the original address signal N ₀ ~N _11). Although the cosine wave is stored in the wave memory 42, even if the wave is a sine wave,
Alternatively, the waveform may be another waveform, and even if waveform information for one cycle is not necessarily stored, a half cycle of the waveform or 1 / The information of one cycle of the waveform can be reproduced only by storing the information of four cycles in the memory.

In this case, a cosine wave signal is generated from the waveform memory 42 with the amplitude value represented by 8 bits. The signal is sent from the output terminals O _{0 to} O _{7 and} is input to the B input terminal (B ₀
Is supplied to the ~B _7). The envelope signal from the envelope signal generation circuit 44 is supplied to the A input terminals (A _{0 to} A ₇ ) of the multiplication circuit 43.

That is, in the envelope signal generation circuit 44, among the address signals N ₀ to N _11, the upper 9 bits signal is supplied.
That is, the most significant bit signal N ₁₁ of the address signal is supplied in common to one input terminal of the NAND gate 44-0～44-7 in the envelope signal generation circuit 44, also the NAND gate of each
The other input terminal of 44-0～44-7, address signal N ₃ to N
₁₀ are each supplied. And this NAND gate 44-0
The outputs of .about.44-7 become envelope signals and are supplied to the A input terminal of the multiplication circuit 43 as described above.

The multiplying circuit 43 outputs a signal (referred to as A) from the A input terminal.
And (a B) signals from B input and the value obtained by multiplying the 2 ^-8, that is, the value of A × B ÷ 2 ⁸ outputs.

Then, the multiplied output is applied to the output terminal 0, and thereafter is also supplied to the envelope multiplying circuit 8 shown in FIG.

Next, FIG. 3 shows an operation state of the present embodiment when the modulation signal supplied from the adder circuit 6 is at the maximum level FF (in hexadecimal notation). the via and multiplying circuit 41 the address signal N (N ₀ ~N ₁₁₎ to be supplied to have the meanings indicated changes in the hexadecimal representation 000 during one period which is determined according to the frequency of the output tone It changes up to FFF.

Then, an output Q as shown in FIG. 3 (b) is obtained from the multiplication circuit 41. That is, since the modulation signal is FFF, the multiplication circuit 41 generates a modified address signal that changes from 00 to FF at a rate of 16 times in one cycle.

FIG. 3C shows a waveform signal generated by the waveform memory 42 addressed by the corrected address signal, and the output waveform signal is supplied to the multiplication circuit 43. The multiplication circuit 43 further receives an envelope signal as shown in FIG.
It is given by changing as follows.

That is, the output of the NAND gate 44-0～44-7, in one period of the waveform, the period of the first half (period of the most significant bit N ₁₁ is "0" of the address signal), the maximum level FF (16 hexadecimal representation) It holds, that in the second half of the period (the period of the most significant bit N ₁₁ is "1" of the address signal), so that successively changes from the maximum level to the minimum level 00.

Therefore, the output of the multiplying circuit 43 is as shown in FIG. 3 (e), and the waveform signal generated in one cycle of the waveform is level-controlled by the envelope signal to be generated.

FIG. 4 shows a waveform signal under the above conditions (FIG. 4A) and its frequency spectrum (FIG. 4B).

FIGS. 5 (a) and 6 (a) show waveforms when the magnitude of the modulation signal M in FIG. 4 is set to 1/2 and 1/4, respectively. FIG. 6 (b) shows the frequency spectrum at that time, and it is understood that the eighth and fourth harmonic components are emphasized.

In the embodiment described above, the envelope signal generation circuit
From FIG. 44, an envelope signal as shown in FIG. 3 (d) was generated. However, the present invention is not limited to this. The maximum level is taken for a predetermined period in one cycle of the waveform, and from the maximum level to the minimum level in other periods. Alternatively, any signal that generates an envelope signal that changes from the minimum level to the maximum level may be used.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to realize a resonance effect in which a specific harmonic component is emphasized with a simple circuit configuration, and to obtain a waveform having one or more cycles obtained in one cycle of the waveform. In order to obtain an output waveform signal by multiplying the signal by a maximum level during a predetermined period in one cycle of the waveform, and multiplying by an envelope signal that sequentially changes from the maximum level to the minimum level or from the minimum level to the maximum level during other periods, It is possible to obtain a waveform signal containing a harmonic component unique to the envelope signal.

Also, by changing the modulation signal that determines the number of waveform signals generated in one cycle of the waveform with time, the harmonic component having a peak in the amplitude characteristic can be sequentially changed with time, similar to an analog music synthesizer. This has the advantage that the resonance effect can also be obtained.

[Brief description of the drawings]

1 shows an embodiment of the present invention, FIG. 1 shows a block circuit thereof, FIG. 2 shows details of a waveform generation circuit of FIG. 1, and FIG. 3 shows the operation of this embodiment. FIGS. 4 to 6 are signal diagrams for explaining the waveform signal obtained by this embodiment and the frequency spectrum thereof. 2 ... frequency information generation circuit, 3 ... phase angle calculation circuit, 4
…… Waveform generation circuit, 5 …… Modulation signal generation circuit, 41, 43…
... Multiplication circuit, 42... Waveform memory, 44... Envelope signal generation circuit, 44-0 to 44-7.

Claims (2)

(57) [Claims] A storage means for storing waveform information; an address signal generation means for sequentially generating an address signal for reading the waveform information stored in the storage means; and the waveform information stored in the storage means. Automatically modulates the modulation signal for modulating the address step speed at the time of addressing and reading with the address signal as a signal whose content changes continuously with the passage of time from the start of generation of a musical tone. The generated modulation signal generation means: multiplies the address signal output by the address signal generation means and the modulation signal output by the modulation signal generation means, so that the address signal specifies an address of one cycle of the waveform. Means for obtaining a correction address for specifying an address of more than one cycle of the waveform, and An access unit for accessing the storage unit with the corrected address signal, and a periodicity for determining a frequency of a generated musical tone based on the address signal output by the address signal generation unit,
An envelope signal generating means for generating an envelope signal that takes a maximum level for a predetermined time within this one period and changes from the maximum level to the minimum level or from the minimum level to the maximum level during the other period; and Multiplying means for multiplying the waveform information obtained by the access by the envelope signal generated by the envelope signal generating means. The multiplying means comprises: In accordance with the continuous change of the content, the frequency of the waveform included in one cycle of the waveform determined by the envelope signal automatically changes with the passage of time from the start of generation of the musical tone. Musical sound generator. 2. The method according to claim 1, wherein said envelope signal generating means commonly inputs a most significant bit of said address signal to a first input terminal,
2. A tone waveform generator according to claim 1, wherein said input terminal comprises a plurality of NAND gates for respectively inputting address signals of lower bits than said most significant bit.