JPH0128399B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic musical instrument that uses a carrier wave as an arbitrary waveform containing harmonic components, and synthesizes musical tones by reading out the frequency modulated waveform from a waveform function table.

Conventionally, in the method of synthesizing musical tones by frequency modulating a carrier wave, the modulation sideband forms harmonic overtones or non-harmonic overtones of the carrier wave, and when the fundamental frequency of the musical tone matches the carrier wave frequency, the sideband of the frequency modulated carrier wave It takes advantage of the property that wave bands form overtones of musical tones. This method has the advantage that the overtone structure of the waveform can be easily created using fewer parameters than the conventional addition method using sine synthesis, and that these can be easily changed. A musical tone synthesis method using frequency modulation is described in Special Publication No. 49-31894 or J.
Aud.Eng.Soc.Vol.21, No.7 September 1973 526~
It is described in the paper published on page 534: ``Synthesis of complex audio spectra by frequency modulation'' by G. M. Chiyoning. Additionally, Japanese Patent Application Laid-Open No. 126406/1983 discloses a digital system for putting this frequency modulation theory into practice, and Japanese Patent Application No. 164504/1983 also proposes a system for putting this into practice. ing.

The spectral patterns in these musical tone synthesis methods using frequency modulation depend on the Betzel function, and have characteristics such as a sharp decrease in high-order spectral components. Compared to the addition method using synthesis, this method is good for lead sounds, but has the disadvantage that it cannot produce satisfactory results for synthesizing other string sounds and other natural instrument sounds. As a result of our studies, the present inventors found that this drawback is due in part to the fact that the frequency-modulated wave musical tone synthesis method uses only the fundamental wave (sine wave) as a carrier wave, and harmonic components It has been found that by including a variety of natural musical instrument sounds or musical sounds similar to these, it is possible to obtain even more diverse sounds.

An object of the present invention is to provide an electronic musical instrument that synthesizes various natural musical instrument sounds using a method of synthesizing musical tones by frequency modulating carrier waves.

To achieve the above object, an electronic musical instrument that synthesizes musical tones by frequency modulation includes timbre control means for generating timbre control data selected by means for selecting the timbre of the generated musical tones, and an arbitrary waveform as a modulated wave. a first storage means for storing, a second storage means for storing an arbitrary waveform including a harmonic as a carrier wave, a means for determining the angular velocity of the carrier wave, and a first timbre control data from the timbre control means. modulation index generating means for generating a modulation index that changes over time; and a modulation index generating means for reading out a modulated wave signal from the first storage means in response to second timbre control data output from the timbre control means. 1 readout means, and the second storage by the modulated wave signal read out by the first readout means, the modulation index from the modulation index generation means, and the signal from the means for determining the angular velocity of the carrier wave. and second readout means for reading out a carrier wave signal from the means.

The principle and embodiments of the present invention will be explained in detail below.

The general formula for the frequency modulation waveform is expressed by the following formula (1).

(t)=A(t)sin( _ωc +I(t) _sinωnt ) (1) where A(t): Carrier amplitude _ωc : Carrier angular velocity I(t): Modulation index _ωn : Modulation The angular velocity of the wave Equation (1) is expressed by the following Equation (2) using the Betzel function.

(t)=A(t) {Jo(I(t)) sinω _c t+J ₁ (
I(t))[sin( _ωc + _ωn )t−sin( _ωc − _ωn )t]+ _J2 (I(t))[sin( _ωc
+2ω _n )t+sin(ω _c −2ω _n )t] 〓 +J _k (I(t))[sin(ω _c +Kω _n )t+(−
1) ^K sin(ω _c −Kω _n )t]}...(2) Here, J _K is the Betzel function of the first kind.

In the present invention, the carrier wave in equation (1) is not limited to a sine wave, but any waveform containing harmonic components can be used to create a desired natural instrument without being limited to the pattern developed in equation (2). It is possible to synthesize musical tones close to .

For example, when a sawtooth wave is used as a carrier wave, the carrier wave is given by equation (3).

(θ)=Aθ/π |θ|<π (3) When (θ) is expanded into a Fourier series as a periodic function of |θ|<π, 9(θ)=2A/π _∞ 〓 ⁿ⁼¹ (-1) ^n-1 /nsinnθ (4).

When frequency modulation is applied to equation (4) using a modulating wave proportional to the period of the carrier wave, as θ=ω _c t+I(t) sinω _n t, S(t)=(θ)=2A/π _∞ 〓 〓 ^{n =1} (-1) ^n-1 /nsinn(ω _c t+I(t) sinω _n t)(
5) Expressing equation (5) as a Betzel function, S(t)=2A/π _∞ 〓 〓 ⁿ⁼¹ (-1) ^n-1 /n{J ₁ (nI(t) sinnω _c t+J ₁ (nI
(t)) [sin(nω _c +ω _n )t−sin(nω _c −ω _n )t]+J ₂ (nI(t)) [s
in(nω _c +2ω _n )t+sin(nω _c −2ω _n )t〕 〓 +J _K (nI(t))[sin(nω _c +Kω _n )t+(−1) ^K si
n(nω _c −Kω _n )〕+…}…(6) Equations (5) and (6) apply frequency modulation to each harmonic component of the sawtooth wave, and are better compared to Equation (2). Creates a signal rich in overtones.

The frequency spectrum of equation (6) is shown in FIG. The figure is a frequency analysis of equation (5), and there is a modulated wave component spectrum around the spectrum of carrier wave frequency c, and modulated wave component spectra are also distributed around the double and triple carrier wave components. Since these spectra are controlled by the modulation index I(t),
By temporally controlling the modulation index I(t),
It is clear that temporal changes in timbre can be added. In the above example, a sawtooth wave carrier wave was used, but the invention is not limited to this, and triangular waves,
It is clear that this method is effective for waveforms including harmonics such as pulse waves and sine composite waves.

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention, which is applied to the example proposed in Japanese Patent Application No. 164504/1983. Here, the waveform used for the carrier wave, for example, the sawtooth wave shown in Fig. 2, is stored in the arbitrary waveform function table 54 described later, and by applying frequency modulation with the signal described below, the waveform as shown in Fig. 3 is obtained. I can get a signal.

In the figure, when the keyboard switch 10 is pressed by the performer, the tone detection and assignment circuit (NDA)
20 detects keyboard information, transmits the keyboard information to the execution control circuit 40, and also transmits the keyboard information to the envelope circuit.
Supply to ADSR (Attack, Decay, Sustain, Release) 60, envelope amplitude A of musical tone
(t) signal and a modulation index I(t) to be described later.

Based on the keyboard information from the NDA 20, the execution control circuit 40 sends a signal for waveform calculation to the sound source circuit 5.
Input into word counter 51 within 0. The word counter 51 is composed of a 32-digit counter and represents the word position of the waveform data. The angular velocity ω _c of the carrier wave is shown on line 503 as the binary data output of the word counter 51.
data is output. Line 503 is adder 52
is input to the multiplier 56. Multiplier 56 is used to determine the angular velocity ω _n of the modulated wave. Information about the tablet selected by the tablet switch 501 is transmitted to the timbre control circuit 502, and the timbre control circuit 502 outputs control data related to the angular velocity of the modulated wave and the modulation index that determine the timbre. Multiplier 56 receives data from tone control circuit 502, multiplies it with data from line 503, and sends data of angular velocity ω _n to memory address decoder 57.

The memory address decoder 57 reads out an arbitrary waveform function table 58 that stores the waveform of the modulated wave. The arbitrary waveform function table 58 is applied and selected not only to orthogonal functions such as sine waves but also to any function of a desired acoustic waveform. When the arbitrary waveform function table 58 stores, for example, a sine wave as shown in FIG. 4, this data is read out by the memory address 57 and input to the multiplier 59. The output of the multiplier 591 is input to the other input of the multiplier 59, and the multiplier 591 is connected to the ADSR6.
0, and the other input receives data from the timbre control circuit 502. The data generated by the ADSR 60 is, for example, data that changes over time as shown in FIG.
It is expressed as This data In(t) is multiplied by data K from the tone control circuit 502, and I(t)=K
×In(t) is calculated. Multiplier 591 output I
(t) and the output of the arbitrary waveform function table 58, for example, a sine waveform, is multiplied by the multiplier 59, and I(t)
sinω _n t is sent to adder 52 .

The adder 52 adds the output ω _c of the word counter 51 and the output of the multiplier 59 to determine the phase angle ω _c t+I(t) sin ω _n t of the carrier wave during frequency modulation. The output of this adder 52 is input to a memory address decoder 53, which reads the fundamental wave and harmonic waveform data in the arbitrary waveform function table 54 storing the modulated waveform of the carrier wave, and reads out the fundamental wave and harmonic waveform data in the main register 53.
Store in 5. The main register 55 is a register having a capacity of, for example, 32 words, and stores a set of calculated waveform amplitude data, that is, a main data set. In the above order, calculated data is stored in each word of the main register 55 each time the value of the word counter 51 is incremented by a signal from the execution control circuit 40.

When the value of the word counter 51 reaches 32 words, the calculation is completed, and the execution control circuit 40 disconnects the main register 55 from the sound source circuit 50, controls it with the tone selector 551, and loads the main data set into the tone shift register (NSR) 80. Forward. NSR80 and NSR81
Each data set has a capacity of 32 words including NSR82, and the main data set is NSR8
1 or NSR82 is selected. The NSR 80 here consists of two registers, NSR 81 and NSR 82, and the number is the same as the number of channels assigned to the NDA 20 or a multiple thereof. The read rate of NSR 81 or NSR 82 is selected by sending a signal determined by tone clock generator 70 to clock selector 31. Digital data read out at that rate is converted into an analog voltage by DAC91 or DAC92 in D/A converter 90. In this case, the envelope voltage A generated from ADSR60 has the shape shown in FIG.
(t) is given as a reference voltage to the DACs 91 and 92 and multiplied by the contents of the NSRs 81 and 82.

Musical sound data converted into analog waveforms by the DACs 91 and 92 are synthesized by a mixing circuit 101, and emitted as audible sound by an amplifier 102 and a speaker.

As explained above, according to the present invention, a waveform including a harmonic component corresponding to an arbitrary waveform is used as a carrier wave, and a waveform corresponding to a frequency modulated wave related to the basic equation and a frequency modulated waveform of the carrier wave is used as a waveform. This is stored in a function table, read out, and computationally synthesized.As shown in Figure 7, it contains much more harmonic components than when the carrier wave is only the fundamental wave, and is useful for lead systems. This makes it easy to synthesize musical tones that are close to the sounds of not only string instruments but also various natural instruments such as piano.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing the configuration of an embodiment of the present invention,
2 to 6 are operational waveform diagrams of the main parts of the embodiment, and FIG. 7 shows an example of the frequency spectrum of the present invention. In the figure, 10 is a keyboard switch, 20
30 is a main clock, 31 is a clock selection circuit, 40 is an execution control circuit, 50 is a sound source circuit, 501 is a tablet switch, 502
51 is a timbre control circuit, 51 is a word counter, 52 is an adder, 53 is a carrier wave memory address decoder, 5
4 is a carrier wave arbitrary waveform function table, 55 is a main register, 551 is a tone selection circuit, 56, 59, 591
is a multiplier, 57 is a memory address decoder for modulated waves, 58 is an arbitrary waveform function table for modulated waves, 60 is an envelope circuit (ADSR), 70 is a tone clock generator, 80, 81, 82 are tone shift registers,
90, 91, 92 are digital-analog converters,
101 is a mixing circuit, and 102 is an amplifier.

Claims (1)

[Claims] 1. An electronic musical instrument that synthesizes musical tones by frequency modulation, comprising: timbre control means 502 that generates timbre control data selected by means for selecting the timbre of the generated musical tones, and an arbitrary waveform as a modulated wave. a first storage means 58 for storing an arbitrary waveform including a harmonic as a carrier wave; a means 51 for determining the angular velocity of the carrier wave; and a first storage means 58 for storing an arbitrary waveform including a harmonic as a carrier wave; Modulation index generating means 591, 60 for generating a modulation index that changes over time based on timbre control data; first reading means 56, 57 for reading a modulated wave signal; and means for determining the modulated wave signal read by the first reading means, the modulation index from the modulation index generating means, and the angular velocity of the carrier wave. an electronic musical instrument, comprising: second reading means 52, 53, 59 for reading carrier wave signals from the second storage means according to signals from the second storage means.