JPS6112279B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic musical instrument, and more particularly to an improvement of a digital electronic musical instrument using a so-called frequency modulation method as a basic method for forming musical tones (hereinafter referred to as the FM method).

A conventional FM digital electronic musical instrument is disclosed in Japanese Patent Application Laid-open No. 126406/1983.

This digital electronic musical instrument uses an FM modulation method based on a sine wave as a musical tone calculation formula e=A sin(ωct+I(t)sin ωmt)
... (1) is used to change parameters such as I(t) over time to make the calculated signal e into a predetermined musical sound waveform.

However, when calculating the instantaneous value of a musical tone at each sampling point based on equation (1), normally two sine wave tables, for example, in ROM configuration, are prepared, and one of them is used to calculate I( t) sin
The term ωmt is calculated, and by the other hand, the equation (1) is
The term Asin(ωct+I(t) sin ωmt) is calculated. Therefore, according to the conventional electronic musical instrument, two sine wave tables must be prepared, and therefore there is a limit to the simplification of the structure.

In addition, since equation (1) is based on the idea of transforming the sine waveform in principle, the musical tone, which is made by connecting the instantaneous values at each sampling point over time, does not contain too many harmonic components. . This means that there is little freedom in selecting timbres when it is desired to add a desired timbre to the musical tones thus formed, and this is still insufficient considering the demands of electronic musical instruments to create a wide variety of timbres. be.

In consideration of the above points, the present invention does not require a large capacity memory for storing tables in advance as in the conventional case, and moreover, it is possible to create musical tones with significantly more complex tones compared to the conventional method. The aim is to realize a digital electronic musical instrument that can be created.

An example of an electronic musical instrument according to the present invention will be described below in detail with reference to the drawings. In the case of the present invention, each instantaneous value of a musical tone is calculated using a basic formula in the same format as the FM modulation formula expressed by formula (1) above. It is similar to the conventional method, but its distinctive feature is that a triangular waveform is used as the waveform of the fundamental wave.

That is, in this invention, musical tones are formed using the following arithmetic expression.

e=T{α+A·T(θ)} (2) Here, θ is the phase angle of the modulation signal, which changes periodically at a predetermined repetition rate. T(θ) is a modulation signal made of a triangular wave function that is repeatedly generated with a repetition period of θ. A is the modulation index for the modulation signal T(θ). α represents the phase angle of the musical tone to be generated, and changes periodically at a predetermined repetition rate. T{α+A·T(θ)} represents each instantaneous value of a musical tone signal formed by a triangular wave function that changes periodically at a repetition rate of α.

An electronic musical instrument that forms musical tone signals by calculating equation (2) has a musical tone forming circuit 1 having a basic configuration as shown in FIG.

2 is a triangular wave generation circuit, which generates a sawtooth waveform phase angle signal Sθ consisting of 10-bit digital signals _b0 to _b9 .
(represented by 2'S complement),
It sends out a triangular wave output S1 consisting of 9-bit digital signals _a0 to _a3 , and for example, the configuration shown in FIG. 2 can be applied.

That is, the triangular wave generating circuit 2 includes eight exclusive OR circuits EX0 to EX7 which receive the 0th to 7th bits _b0 to _b7 of the phase angle signal Sθ as one input, and the eighth exclusive OR circuit EX0 to EX7.
and one exclusive OR circuit EX8 receiving the ninth bits _b8 and _b9 , and this exclusive OR circuit
Output P of EX8 is exclusive OR circuit EX0 to EX7
is given as the other input. Then, the outputs of the exclusive OR circuits EX0 to EX7 are sent out as the 0th to 7th bits _a0 to _a7 of the triangular wave output S1,
The ninth bit _b9 of the phase angle signal Sθ is sent out as is as the eighth bit _a8 of the triangular wave output S1.

Here, the triangular wave generation circuit 2 generates digital sawtooth wave-like phase angle signals Sθb ₉ to b ₀ as shown in FIG. 3A.
As shown in FIG. 3B, during the period from "0000000000" to "11111111", there is a triangular waveform part TA that rises in the raw direction and then falls, and a triangular waveform part TB that falls in the negative direction and then rises. As the phase angle signal Sθ changes from "0000000000" to "1111111111" as shown in FIG. 4, the output P of the exclusive OR circuit EX8 changes from "0" to "1" to "0". ", and by matching this output P with the 0th to 7th bits _b0 to _b7 of the phase angle signal Sθ, the 0th to 7th bits of the triangular wave output S1
The contents of the seventh bits _a0 to _a7 are made to be the same, and together with this, the ninth bit _b9 of the phase angle signal Sθ is sent out as the eighth bit _a8 of the modulated signal output S1.

In this way, as shown in FIG. 3B, the triangular wave output S1 becomes positive when the content of the eighth bit _a8 is "0" and negative when the content is "1", and the output P of the exclusive OR circuit EX8 As shown in FIG. 4, when is "0" (range 1, 4), the triangular wave output S1 increases,
When it is "1" (range 2, 3), it will decrease.

In this way, the 9-bit triangular wave output S1 generated at the output terminal of the triangular wave generating circuit 2 and varying as shown in FIG. The signal is input to the multiplier circuit 3 as a multiplicable signal. Here the modulation index signal
SA gives the modulation index A of equation (2), and is composed of a digital signal of a predetermined number of bits as required. Therefore, at the output terminal of the multiplier circuit 3, a triangular wave output S2 as shown in FIG. Become.

This triangular wave output S2 is the second term A・T in equation (2).
(θ) is input to the bit number increasing circuit 4.
It is input to the bit number increasing circuit 4. The bit number increasing circuit 4 adds "0" in binary to the lowest bit (LSB) of the 9-bit triangular wave output S2.
bits are added, thereby sending out a 10-bit triangular wave output S3. The reason why such a bit number increasing circuit 4 is provided is to match the number of bits of two signals when they are added together in the next step.

The triangular wave output S3 of this bit number increasing circuit 4 is
It is applied to the adder circuit 5 as one addition input.
This adder circuit 5 executes the calculation in { } of the above equation (2), and calculates the phase angle signal Sα (2'S expressed as complements)
is given as the other addition input. Here, the phase angle signal Sα is from "0000000000" to "0000000000" as shown in FIG.
It changes repeatedly between "1111111111" at a scheduled cycle. Therefore, the adder circuit 5 has a period in which the period of the phase angle α is increased or decreased by the triangular wave output S3, and the content is α+A·T(θ) that changes between “00000000000” and “11111111111” in binary. An 11-bit digital signal output S4 is obtained.

This output S4 is given to the second triangular wave generating circuit 6. This triangular wave generating circuit 6 has the same configuration as the triangular wave generating circuit 2 described above with reference to FIG. Note that the output S4 of the adder circuit 5 is 11 bits, but in order to convert this to 10 bits, the lower 10 bits of the output S4 are input S4 to the second triangular wave generating circuit 6.
5.

However, this triangular wave generating circuit 6 generates a triangular wave T{α+A·T in the same manner as described above with reference to FIG.
(θ)} is sent out as a musical tone signal S6 that satisfies equation (2) above.

The musical tone format circuit 1 having the structure shown in FIG. 1 is operated by a key switch of a keyboard circuit 11 as shown in FIG.

In this embodiment, the keyboard circuit 11 has 61 key switches corresponding to each of the 61 keys, and the key output KN consisting of 61 line outputs generated from each key switch is stored in a frequency information memory (ROM) 12. is given as an address signal.

At this time, the frequency information memory 12 outputs frequency information (numerical value) F corresponding to the input key output KN.
θ and Fα are input to accumulators 13 and 14 as signals representing the phase angle θ of the modulation signal and the phase angle α of the musical tone, respectively. Accumulators 13 and 14 receive frequency information outputs Fθ and Fα and repeatedly accumulate the clock pulse signal φ in ₀ cycles, and the accumulated results are used as modulation signals and musical tone phase angle signals Sθ and Sα, respectively, in the musical tone forming circuit 1 of FIG. Enter.

On the other hand, when a key is pressed on the keyboard, the keyboard circuit 11 generates a key-on signal KON indicating that the key is in a pressed state, and this is sent to the modulation index generation circuit 15.
give to The modulation index generation circuit 15 generates a key-on signal.
A modulation index signal SA containing a modulation index A whose value changes over time is generated in order to change the timbre of the musical tone from the time when KON arrives until it ceases to arrive due to key release, and this modulation index signal SA is generated. The exponential signal SA is applied to the multiplication circuit 3 shown in FIG.

Thus, the musical tone forming circuit 1 has a pitch corresponding to the key pressed on the keyboard (mainly determined by the phase angle signal Sα), and a tone corresponding to the pressed key (mainly determined by the phase angle signal Sα). Phase angle signal S
(determined by θ), a musical tone signal S6 having a predetermined timbre change is generated after the key is pressed and until the key is released.

This musical tone signal S6 is transmitted to the envelope generating circuit 16.
is given as a multiplicable signal to a multiplier circuit 17 that receives the envelope signal EN from as a multiplier signal,
In this way, the musical sound signal S6 is given an envelope that rises rapidly when the key is pressed, passes through the sustain section, and decays when the key is released, and is then converted into a musical tone by the sound system 18 and emitted as a musical tone. In this embodiment, the sound system 1
Reference numeral 8 includes a D/A converter that converts the musical tone signal S6, which is a digital signal, into an analog signal, an amplifier that amplifies the output thereof, and supplies the amplified signal to a speaker.

As described above, according to the configurations shown in FIGS. 1 to 6, musical tones can be formed based on the above-mentioned equation (2).

Although two triangular wave generating circuits 2 and 6 are used as the musical tone forming circuit 1 in FIG. 1, an embodiment of the present invention in which only one triangular wave generating circuit is required is shown in FIG. In FIG. 7, parts corresponding to those in FIG. 1 are designated by the same reference numerals.

In this case, the phase angle signal Sθ of the modulation signal is inputted via the input selection circuit 21 to the triangular wave generation circuit 22 having the same configuration as that described above with reference to FIG. This input selection circuit 21 has a first input terminal T to which a phase angle signal Sθ is applied when one of a pair of selection load signals φ _A and φ _B is inputted by φ _A.
The first side is connected to the triangular wave generation circuit 22, and when the selection load signal φ _A has not arrived, the second
The input terminal T2 side of the input terminal T2 is connected to the triangular wave generation circuit 22.

Here, the selection load signal φ _A is a square wave that rises at predetermined time intervals as shown in FIG. 8A, and its rising portion is the rising edge of the other selection load signal φ _B shown in FIG. 8B. It is designed to occur in the interval between.

However, when the selection load signal _φA is generated and the phase angle signal Sθ is input to the triangular wave generating circuit 22, the output of the triangular wave generating circuit 22 is given to the multiplier circuit 3, the bit number increasing circuit 4, and the adding circuit 5. . Therefore, at the same time as described above in FIG.
(θ)} is generated.

In this embodiment, this signal S4 is
and select the load signal φ as the load signal.
This signal S, provided that _A is given
4 is stored in register 23. However, the number of bits in the memory contents of the register 23 is changed in the same way as in FIG. 1 when the output S4 of the adder circuit 5 is changed from 11 bits to 10 bits when inputting it to the triangular wave generating circuit 6, and the signal S5 is inputted. Selection circuit 21
is applied to the second input terminal T2 of.

The above system is a system that operates when the selection load signal φ _A arrives, but eventually the selection load signal φ
When _A is no longer input, the input selection circuit 21 performs a switching operation and the signal S5 applied to the second input terminal T2 is applied to the triangular wave generation circuit 22. Therefore, as a result of the calculation in the triangular wave generation circuit 22, the formula T
A musical tone signal S6 having the content {α+A·T(θ)} is obtained, but it is not stored in the register 23 because the selection load signal φ _A has not arrived at this time.

However, when the selection load signal φ _B arrives, the register 24, which receives this as a load signal, captures and stores the musical tone signal S6. In this way, the contents stored in the register 24 are sent out as the output of the tone forming circuit 1.

Based on the above selection load signal φ _A , the formula {α+A・
T(θ)} operation and selection load signal φ _B
The calculation and formation operation of the musical tone signal formula T{α+A·T(θ)} is repeated each time the signals φ _A and φ _B arrive alternately.

According to the configuration of FIG. 7, it is possible to obtain the same effect as described above with respect to FIG. 1, but in addition, compared to the case of FIG. be able to.

As described above, according to the present invention, it is possible to digitally generate musical tones using the FM modulation method, but by using a triangular wave for both the modulation wave and the carrier wave, the basic principle can be improved. Therefore, the degree of freedom in selecting harmonic components that can be employed when trying to obtain musical tones with various tones can be expanded.

In addition, in this invention, when forming a musical tone signal according to the above-mentioned equation (2), one triangular wave generation circuit is used in time division for modulation wave generation and carrier wave generation. α+A・T
(θ)} and then T{α+A・T
Since the term (θ)} is calculated, only one triangular wave generation circuit is required, which simplifies the configuration. Moreover, as shown in the embodiment, this triangular wave generation circuit is constructed from a relatively simple data processing circuit without using memory (table), so the construction of an electronic musical instrument (musical tone forming circuit) is greatly simplified. can be converted into

[Brief explanation of the drawing]

Fig. 1 is a system diagram showing the basic configuration of a musical tone forming circuit which is a main part of an electronic musical instrument according to the present invention, Fig. 2 is a connection diagram showing its triangular wave generation circuit, and Figs. 6 is a system diagram showing the overall configuration of the electronic musical instrument according to the present invention, FIG. 7 is a system diagram showing another example of the musical tone forming circuit, and FIG. 8 is a system diagram showing another example of the musical tone forming circuit. FIG. 3 is a signal waveform diagram for explaining its operation. 1... Musical tone forming circuit, 2, 6, 22... Triangular wave generation circuit, 3, 17... Multiplication circuit, 5... Addition circuit, 11... Keyboard circuit, 12... Frequency information memory, 13, 14... Accumulator, 15...Modulation index generation circuit, 16...Envelope generation circuit, 18...Sound system, 21...Input selection circuit, 23, 24...Register.

Claims (1)

[Scope of Claims] 1. Phase angle generating means for generating a phase angle signal θ indicating the phase angle of a modulation signal and a phase angle signal α indicating the phase angle of a musical tone; and a modulation index generating means for generating a modulation index signal A. , a triangular wave generating means for generating a first triangular wave function signal T(θ) based on the input phase angle signal; and the first triangular wave function signal T(θ) is weighted by the modulation index signal A. and a calculating means for adding the phase angle signal α to the phase angle signal α at a first timing.
is selected and inputted to the triangular wave generating means to generate the first triangular wave function signal T(θ), and the triangular wave function signal T(θ), the modulation index signal A and Signal corresponding to the above phase angle signal α {α+A・T
(θ)}, and at a second timing, the output signal {α+
A.T(θ)} is selected and inputted to the triangular wave generating means to generate a second triangular wave function signal T{α+A.T(θ)} from the triangular wave generating means; The second generated at the timing of
An electronic musical instrument comprising musical tone generating means for generating a musical tone signal based on a triangular wave function signal T {α+A·T(θ)}. 2. The electronic musical instrument according to claim 1, wherein the modulation index signal A is changed over time.