JPS5836798B2 - electronic musical instruments - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic musical instrument, and more particularly to an electronic musical instrument that prevents the timbre of musical sounds from changing due to pitch.

As an electronic musical instrument that keeps the timbre (harmonic content) of musical sounds almost constant regardless of the pitch, the
There is one shown in the specification of No. 9371.

This electronic musical instrument has a variable filter installed in the signal path of the sound source signal, and the characteristics of the variable filter are changed by the output voltage of a frequency discriminator that inputs the sound source signal, thereby generating a musical tone with a constant tone regardless of the pitch. It was designed to do so.

Even with such a configuration, the effect of timbre compensation can be achieved to some extent.

However, it is extremely difficult to completely compensate for variations in timbre due to nonlinearity of a characteristic control element (for example, a field effect transistor) of a variable filter, and it is impossible to achieve complete timbre compensation.

Another problem is that a frequency discriminator must be provided to control the characteristics of the variable filter.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide a new electronic musical instrument that generates musical tones with almost completely uniform timbre regardless of pitch.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of an electronic musical instrument according to the present invention.

In the figure, 1 is a keyboard circuit, 2 is a voltage-controlled variable frequency oscillator (hereinafter referred to as CO), 3 is a musical tone signal generation circuit, 4 is a voltage-controlled amplifier (hereinafter referred to as VCA), and 5 and 6 are audio power amplifier and speaker that constitute the device;
7 and 8 are envelope generators.

When a certain key on a keyboard (not shown) is pressed, a pitch voltage corresponding to the key is output from the keyboard circuit 1, and the oscillation frequency of the VCO 2 is controlled by this pitch voltage.

The oscillation output of the VCO 2 is supplied to the musical tone signal generating circuit 3 as a clock.

The output of the musical tone signal generating circuit 3 is inputted to a power amplifier 5 via a VCA 4, and after power amplification is performed, a musical tone is produced from a speaker 6.

The envelope generators 7 and 8 generate an envelope voltage in response to a keying signal output from the keyboard circuit 1 during a key press period.

The gain of the VCA 4 is controlled by the output of one of the envelope generators 8, and this gives musical tones temporal amplitude change characteristics similar to those of natural musical instrument sounds, such as attack, fast decay, sustain, and second decay. Ru.

Also, the output of the other envelope generator 7 causes V
The oscillation frequency of CO2 is controlled by a certain amount, giving the musical tone a temporal change characteristic of pitch similar to that of a natural musical instrument.

Note that the keyboard circuit 1, pitch voltage and keying signal, envelope generators 7 and 8, and envelope voltage may be the same as those in a conventional electronic musical instrument, so further explanation will not be given.

The musical tone signal generation circuit 3 changes the fundamental frequency of the generated musical tone signal faithfully following the frequency of the input clock, but the spectrum distribution state (harmonic content) of the musical tone signal changes as the clock frequency changes. It is configured in such a way that it will not change.

Therefore, with the electronic musical instrument of the present invention, a musical tone signal with a constant spectrum distribution state can be obtained no matter which key is pressed, and therefore a musical tone with the same tone can be obtained no matter what key is pressed.

The configuration of the musical tone signal generating circuit 3 will be explained below, but first, the switching type digital RC filter will be explained.

FIG. 2 shows an example of a parallel switching type digital RC filter P and its peripheral circuit.

Input terminal Ti and output terminal T of digital RC filter F
A resistor R is connected in series to the signal line between the signal line and the signal line, and four capacitors C are connected between the output terminal To side of the signal line and the ground, respectively, via transistors Tr.

These transistors Tr can be replaced with other switching elements such as field effect transistors or even mechanical switches.

Further, the number of capacitors C is not limited to four, but any number may be provided.

Each transistor Tr is sequentially turned on at a fixed timing.

In this example, the clock input to the clock terminal Tc is 2
The signal is input to a bit binary counter 21, and the output of each bit of this counter 21 is supplied to a digital RC filter F as a timing pulse.

Decoder 22 provided in digital RC filter F
is the drive pulse S1 based on the above timing pulse.
, S2, S3, S4, and this drive pulse 81
~S4, each transistor Tr is sequentially driven.

The timing relationship between each drive pulse S, -S4 and the clock is as shown in FIG.

Note that the digital RC filter F in this example is the decoder 22.
However, the timing pulse is applied to each transistor T
In the case of a configuration in which r can be directly driven, the decoder 22 is not necessary.

This digital RC filter F exhibits a comb-like filter characteristic having a large number of pass bands b as shown in FIG.

The center frequencies of each passband b are harmonically (integral multiples) related to each other, and the timing pulses or drive pulses S, ~
This corresponds to each harmonic frequency of S4.

The bandwidth BW of each pass band b is expressed as follows, and is determined by the values of the resistor R and capacitor C.

Further, the relative gain A at the center frequency of each pass band b is expressed as follows.

However, sampling interval γ=E sample 1
The digital RC filter F of this example has a 4°g period T = 7pr (see Figure 3). As is clear from equation (2) and Figure 4, the digital RC filter F of this example
4 times the frequency 4f, an integral multiple of the frequency 4fp-8fp,
There is no pass band for 12fp-.

Note that equations (1) and (2) can be generalized as follows.

However, N is equal to the number of capacitors C, and the clock frequency is Nf.

As mentioned above, a switching digital RC filter has a large number of passbands with a center frequency equal to each harmonic frequency of the timing pulse. Furthermore, even if the frequency of the timing pulse is changed, the above relationship does not change, and the relative gain of each passband remains unchanged.

In addition to the parallel switching type, there are also series switching types as switching type digital RC filters, and both can be applied to the present invention.

Note that such digital Re filters are described in various documents,
For example, the July 24, 1967 issue of the American magazine Electronics, pages 91 to 1.
Since it is introduced on page 00 and is already known, no further explanation of the operating principle, modifications, etc. will be given.

FIG. 5 shows an example of the musical tone signal generating circuit 3. As shown in FIG.

In the same figure, Fo, F1, ......, F
n-1 is a switching type digital RC filter, each having the same configuration as the digital RC filter F in FIG.

The (n+1) bit pinary counter 31 receives a clock (frequency is 2n) applied to the clock input terminal IN.
+1, fp), and each digital RC filter F.

, F1, . . . , F n −1 timing pulses are generated.

The output of the first bit and the second bit of this pinary counter 31, the output of the second bit and the third bit,...
. . . The outputs of the n-th bit and the (n+1)-th bit are respectively output from each digital RC filter F.

, F1, . . . Fn- as a timing pulse.

The digital-to-analog converter 32, together with the pinary counter 31, converts each digital RC filter F based on the clock.

, F1, . . . , Fn timing pulses.

This digital-to-analog converter 32 receives the output of each bit of the pinary counter 31 and converts it into the lower left corner of FIG.
A step-like analog signal with a repetition period of 1/fp as shown in FIG.

Of course, each digital RC filter F is applied to this analog signal.

, F1 . . . . Each harmonic component of the timing pulse of F n-1 is included.

This analog signal is sent to each digital RC filter F.

,F,,......z F n 1 s
is commonly input to each digital RC filter F.

, Fly ......F n-1 output is a variable resistor R as an addition resistor.

, R1, . . . , Rn-1, and then taken out as a musical tone signal from the output terminal OUT.

Next, the operation of this musical tone signal generating circuit 3 will be explained.

If the frequency of the input clock is 2n+1・f, then the first
digital RC filter F.

The frequency of the timing pulse supplied to is 2°·fp,
21 fp, this digital RC filter F
.

The drive pulse generated inside (81 + in Figure 2)
82 + 83 t (corresponding to 84) has a frequency of 2
It becomes 0.fp.

Therefore, this digital RC filter F.

have center frequencies f,,2fp,3fp,'')
fp,6f,,'tf,,9f,,,. ．． ．． ．． ．． ．．・・・
It exhibits comb-like filter characteristics consisting of a large number of pass bands.

Also, the second digital RC filter F1 has a frequency of 21.
Since the timing pulses f, , 22·f, are supplied, the center frequencies of this digital RC filter F are 2f, 4f, 16f, 1of, 12/P, 14fP, 18f, respectively.
It exhibits comb-like filter characteristics consisting of a large number of pass bands P, . . . .

Similarly, the digital RC filter F n-1 has center frequencies of 2n-1·f, 2n-f, 2n+l-
fp,2n+3・pp f ,2n+4.1 ,2n+5,7',,,pp 2n+7・f ,2n+8・f ,・・・・・・・・・
It exhibits comb-like filter characteristics consisting of a large number of passbands pp.

The harmonic components of each timing pulse included in the analog signal created by the digital-to-analog converter 32 are processed by each digital RC filter F() r Fl y...
......, variable resistors Ro, R1, ...... extracted according to the filter characteristics of F n-1.
, Rn-1 and output to the output terminal OUT.

That is, a musical tone signal consisting of harmonic components of each timing pulse is obtained at the output terminal OUT.

And each digital RC filter F. ,F1,...
......, The relationship between the center frequency of each pass band of F n-1 and the frequency of the clock always holds even if the clock frequency is changed, and the relative gain of each pass band is also the same as that of the clock. The analog signal obtained by the digital-to-analog converter 32 is constant regardless of the frequency of the clock, and the analog signal obtained by the digital-to-analog converter 32 is always connected to each digital RC filter F even if the clock frequency is changed.

, F1, . . . , Fn-1, and the relative level of each harmonic component is always constant.

So this musical tone? According to the signal generating circuit 3, a musical tone signal consisting of a plurality of different frequency components that are in a harmonic relationship with each other can be obtained based on a single clock, and moreover, the relative level of each frequency component can be kept constant while each frequency or The frequency of the clock can be changed arbitrarily by changing the frequency of the clock.

In other words, the fundamental frequency of the musical tone signal obtained by this embodiment changes in accordance with the clock frequency, but the state of the spectrum distribution with respect to the fundamental frequency of this musical tone signal is constant regardless of the clock frequency.

Thus, according to the electronic musical instrument of the present invention, a musical tone signal with a uniform tone can be obtained no matter which key on the keyboard is pressed.

The state of the spectrum distribution of the musical tone signal, that is, the tone of the musical tone emitted from the speaker 6 of the audio device, is determined by the variable resistor R.

, R1, . . . , Rn-1 are adjusted to form each digital RC filter F.

It can be changed by changing the mixing ratio of the outputs of F1, . . . , F n-1.

Now, in the musical tone signal generation circuit 3 described above, since the frequency dividing means for generating the timing pulse is a pinary counter, the frequency of the obtained timing pulse is a frequency that is a power of 2 of f, that is, fp, 2fp, 4fp, 8fp
, 16fp, . . .

Similarly, since the digital-to-analog conversion means that generates the analog signal manually input to each digital RC filter is composed of a pinary counter and a digital-to-analog converter, the frequency components included in the analog signal are jp, 2fp. ,4fp ,8fp ,1 6f
It is limited to the frequency precepts of p,...

Therefore, the musical tones obtained from the electronic musical instrument configured using the musical tone signal generation circuit 3 are fp, 2fp, 4fp.
, sfp 16fp , 32fp , ...
It is limited to those consisting of frequency components.

Such restrictions can be overcome by using a musical tone signal generating circuit 3' having a structure as shown in FIG.

In the musical tone signal generating circuit 3' shown in the figure, each digital RC filter F.

, F1, . . . , F n-1 timing pulses are generated by n frequency dividers D.

,D1,...D n-1 and n 1/2
Frequency divider d.

, d1, and song/song d n -1, and each digital RC filter F.

,F,・・・・・・・・・y Fn 3 y Fn
−2 t Fn −1 have the center frequencies of their l-th pass bands f,,? f p ,”・””,(
n-s) f p , (n 2 ) fp, (n-1)
A timing pulse is supplied such that f.

That is, each frequency divider D. tD1”・=・tDn
−s + D n −2 $ D n−t is the frequency 2f p * 4fp +・””””p 2 (n
s)fp,2(n-2)fp,2(n-1)
Outputs fp pulse.

The frequency of the clock input to the clock input terminal IN is determined by each frequency divider D.

, D1, . . . t D n −1 corresponds to the least common multiple of the frequencies of the output pulses.

Conversely, each frequency divider D. ,D1,・・・・・・・・・
, Dn-1 have a frequency division ratio so as to output pulses of a predetermined frequency as described above based on a common clock.

Further, in this embodiment, each digital RC filter F.

, F1, . The signal is generated by a digital-to-analog conversion means comprising a converter 32.

Specifically, when n=2, the frequency divider D.

, D1 s D2 have a dividing ratio of 1/2 and 1/, respectively.
3,1/6, the clock frequency is 12f, and the counter 33 is a hexadecimal counter.

As is clear from the above explanation, in the musical tone signal generation circuit 3' of this example, each digital RC filter F y
F1 s ””””” s F n −3 p F n
-2) The center frequencies of the first pass band of F n-t are f , 2f ,...”..., 2(n
3) fp, pp 2(n 2)/p, 2(n 1) fp, and each digital RC filter F.

,F1,...Fn3tFn
2 s Fn 1 has the frequency fp, 2f p t-
・・・−・・p 2 (n-3) fp t 2 (n
-2)fp, 2(n-1)fp and its harmonic components are input, so it is possible to obtain a musical tone signal having a continuous spectrum distribution.

In this case, in order to change the timbre of a musical tone in accordance with the passage of time from the time of sound generation in the electronic musical instrument shown in FIG. 1, the configuration of the musical tone signal generating device 3 may be partially changed.

Figure 7 shows a musical tone signal generator 3'' with such changes.
This shows an example, and the output of the digital-to-analog converter 32 is connected to a newly installed voltage-controlled filter 34.
through each digital RC filter F.

, F1, ......t F n -1.

The filter characteristics, such as the cutoff frequency, of the voltage-controlled filter 34 are changed over time by a control voltage (envelope voltage) output from an envelope generator 35 that operates in response to a keying signal from the keyboard circuit 1.

It is clear that this allows the timbre of musical sounds to change over time.

In FIG. 7, the same parts as those in FIG. 5 are given the same reference numerals.

Note that in the above explanation, the case was explained in which the VCO 2 driven by the pitch voltage from the keyboard circuit 1 was used as a means for forming a frequency signal corresponding to each key input to the musical tone signal generation circuit 3. The invention is not limited to this, but for example, a system in which the output from a sound source circuit (a combination of an oscillator and a frequency divider) that constantly outputs a frequency signal corresponding to each key is selectively opened and closed by key operation. Of course, it is also possible to use the following.

The point is that it is sufficient to supply the musical tone signal generation circuit 3 with a frequency signal corresponding to the operated key as the key is operated.

As described above, the electronic musical instrument of the present invention generates a musical tone signal that includes a fundamental frequency component corresponding to an operating key and its harmonic components, and whose spectrum distribution, that is, harmonic content rate, is constant regardless of the fundamental frequency. Because it is equipped with a musical tone signal generation circuit that changes the pitch? A musical tone with a uniform tone can be obtained regardless of the difference in tone, and since the musical tone signal generating circuit has a digital configuration, tone color adjustment etc. are extremely easy.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the overall configuration of an embodiment of an electronic musical instrument according to the present invention, FIG. 2 is a circuit diagram showing an example of a known switching type digital RC filter, and FIG. FIG. 4 is a timing chart for explaining the operation of the digital RC filter shown in FIG. 1, and FIGS. 5 to 7 are timing charts showing the frequency spectrum of the digital RC filter shown in FIG. FIG. 3 is a block diagram showing a different configuration example of a musical tone signal generation circuit used in an electronic musical instrument according to the invention. 1... Keyboard circuit, 2... Voltage controlled variable frequency oscillator, 3... Musical tone signal generation circuit, 4
...Voltage controlled amplifier, 5, 6... Amplifier and speaker constituting the audio device, 7, 8, 35
...Envelope generator, Fo-Fn
-1... Switching type digital RC filter, 31, 33... Counter, 32...
・Digital to analog converter, R1 to Rn-1・
...Variable resistance, D-Dn-1...
- Frequency divider, d-dn-1...1/2 frequency divider, 34...Variable filter.

Claims (1)

[Claims] 1. A sound source circuit section that outputs a frequency signal corresponding to a pressed key, a musical tone signal generation circuit that receives the output signal of the sound source circuit section and generates a musical tone signal, and an audio device that converts the musical tone signal into a musical tone. The musical tone signal generation circuit includes a switching type digital RC filter, and means for frequency-dividing the output signal of the tone generator circuit section to generate a timing pulse for controlling switching timing of the digital RC filter. and means for receiving the output signal of the tone generator circuit section, generating an analog signal containing harmonic components of the timing pulse, and inputting the generated analog signal to the digital RC filter, the output signal of the digital RC filter being used as the musical tone signal. An electronic musical instrument configured to be input to the above-mentioned acoustic device.