Apparatus for forming chord signal

An arrangement for forming a musical chord signal in which there are provided a frequency divider for root, a frequency divider for minor third, a frequency divider for major third and a frequency divider for fifth or a frequency divider for seventh. These are connected in common and to an input terminal of a tone source signal. The frequency divider for minor third and the frequency divider for major third have a selection circuit for selectively taking out an output signal according to a major chord or a minor chord of music. The input terminal is connected through plural key-switches to the plural tone source signal oscillators. The output terminals of the frequency divider for root, the selective circuit and the frequency divider for fifth or the frequency divider for seventh are connected together through respective gate circuits which are opened and closed by an output pulse signal of a rhythm pulse generator.

BACKGROUND OF THE INVENTION 
This present invention relates to apparatus for forming a chord signal in 
an electronic musical instrument. 
Such an arrangement in the past, has provided plural gate circuits 
connected to plural key-switches. These gate circuits are applied with 
output signals of plural tone source signal oscillators according to a 
chord, so that a chord signal may be taken out by opening these gate 
circuits. Thus, the conventional arrangement is inconvenient in that a 
large number of gate circuits are needed, and wiring connecting between 
respective tone source signal oscillators and respective gate circuits 
becomes complex and costly, and may cause short-circuit trouble. 
The present invention has the object of providing apparatus for removing 
those inconveniences. 
Another object of the present invention is to provide an arrangement of the 
foregoing character which is simple in construction and may be 
economically fabricated. 
A further object of the present invention is to provide an arrangement, as 
described, which may be readily maintained in service, and has a 
substantially long operating life. 
SUMMARY OF THE INVENTION 
The objects of the present invention are achieved by providing that at 
least a frequency divider for root, a frequency divider for minor third, a 
frequency divider for major third, and a frequency divider for fifth, or a 
frequency divider for seventh. These are connected in common to an input 
terminal for a tone source signal, and the frequency divider for minor 
third and the frequency divider for major third are provided with a 
selective circuit for selectively taking out an output signal according to 
a major chord or a minor chord of music. The novel features which are 
considered as characteristic for the invention are set forth in particular 
in the appended claims. The invention itself, however, both as to its 
construction and its method of operation, together with additional objects 
and advantages thereof, will be best understood from the following 
description of specfic embodiments when read in connection with the 
accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS 
FIG. 1 is a block diagram and shows one embodiment in accordance with the 
present invention; and 
FIG. 2 is a block diagram of another embodiment of the present invention. 
DESCRIPTION OF THE PREFERRED EMBODIMENTS 
Referring to the drawings, (FIG. 1) numerals 1-1, 1-2 . . . 1-12 denote 
tone source signal oscillators of different oscillation frquencies, and 
these tone source signal oscillators 1-1, 1-2 . . . 1-12 are connected in 
common to an input terminal A through respective key-switches 2-1, 2-2 . . 
. 2-12. The input terminal A is branched off to be connected to plural 
frequency dividers 3-1 . . . 3-6. The tone source signal oscillators 1-1, 
1-2 . . . 1-12 oscillate at comparatively high frequencies corresponding 
to respective tones of twelve scales as shown in the drawings. As clearly 
shown in the drawings, the respective frequency dividers 3-1 . . . 3-6 
comprises divisions 506, 426 . . . 284 in frequency ratio so that the 
oscillation frequency of each of the tone source signal oscillators 1-1 . 
. . 1-2 may be frequency-divided into relations of root, minor third, 
major third, fifth, sixth and seventh. The frequency dividers for minor 
third and major third 3-2, 3-3 are provided at their output terminals with 
a selective circuit 4 for selectively taking out an output of either one 
according to a minor (Mn) or a major (Mj) of said music. Output terminals 
of the selective circuit 4 and the frequency dividers 3-1, 3-4, 3-5, 3-6 
are connected together through respective gate circuits 5-1 . . . 5-5, and 
they are further connected to a speaker through a frequency divider for 
bass tone 6, an envelope circuit 7, a filter circuit 8 and an amplifier 
(not illustrated). The frequency divider 6 is omitted if a bass tone is 
not required. Numeral 4a denotes a selective switch provided on the 
selection circuit 4. 
The gate circuits 5-1 . . . 5-5 are connected at their control terminals to 
a rhythm pattern pulse generator 9 so that the same may be controlled to 
open and close by a rhythm pulse signal previously programmed in the 
rhythm pattern pulse generator 9. 
If, now, the switch 2-1, for instance, is closed, the frequency dividers 
3-1 . . . 3-6 are applied with a signal of the frequency 1059.1 KHz (C), 
and the signal is frequency-divided, according to the respective frequency 
dividing ratios, into relations of root, minor third, major third, fifth, 
sixth and seventh. If the selection switch 4a is in its closed condition 
as illustrated, the signal of the major third is obtained at the output 
terminal of the selective circuit 4, and thus there is obtained, as a 
whole, signals of C(Mj). These signals serve to obtain from the speaker, 
rhythm tones of C(Mj) opening the gate circuits 5-1 . . . 5-5 according to 
rhythm pulses supplied from the rhythm pattern pulse generator 9. 
If the selective switch 4a is opened, the signal of minor third is obtained 
and thereby as a whole rhythm tones of C Mn can be obtained. By, further, 
selectively closing any of the remainder switches 2-2 . . . 2-12 and by 
selectively closing the selection switch 4a, any of rhythm tones of Mj or 
Mn in regard to the B . . . C# can be obtained as desired. 
Referring to the drawings, numeral 10 denotes a mixing circuit for mixing 
the output signals of root, third and fifth, and an output terminal 
thereof is connected to a speaker through a gate circuit 11. The latter is 
arranged to be opened by a rhythm pulse signal supplied from the rhythm 
pattern pulse generator 9, and a filter 12, so that the foregoing signals 
of Mj or Mn can be obtained as a chord. Numeral 18 denotes an envelope 
circuit. 
Numerals 13-1 . . . 13-3 denote gate circuits arranged to be controlled to 
open and close in order by output pulses of the rhythm pattern pulse 
generator 9. Input terminals thereof are connected to the output terminals 
for the signals of root, third and fifth, and output terminals thereof are 
connected in common for being connected to an input terminal of a counter 
circuit 14. The counter circuit 14 comprises plural 1/2 frequency dividers 
14-1, 14-2 . . . 14-3 connected in series, and output terminals of these 
frequency dividers 14-1, 14-2 . . . 14-5 are individually connected to 
gate circuits 15-1, 15-2 . . . 15-5 arranged to be controlled to open and 
close in order at every bar of the foregoing rhythm pattern of the rhythm 
pattern pulse generator 9. Output terminals thereof are connected together 
to be connected to a speaker through an envelope forming circuit 16 and a 
filter circuit 17. Accordingly, while the gate circuits 13-1, 13-2, 13-3 
are once opened in order, the gate circuit 15-1 is kept open, and while 
the gate circuits 13-1, 13-2, 13-3 are opened in order in the second 
place, the gate circuit 15-2 is kept open. Similar operations are carried 
out one after another in regard to the gate circuits 15-3, 15-4, 15-5, and 
thus an orpeggio automatic performance can be effected. 
It is possible that the foregoing three kinds of the musical tones are 
simultaneously obtained and that the same are separately obtained. 
The above has been explained with reference to the case that musical tone 
signals of sixth and seventh can be also obtained simultaneously, but 
these tone signals may be omitted, and they can be so modified that a 
musical tone signal of seventh is obtained instead of that of fifth. 
If, in the embodying example shown in FIG. 1, the oscillators 1-1 . . . 
1-12 are arranged to be independently oscillated, an error arises in 
oscillation frequency and accordingly, it is required to synchronize these 
oscillators. For satisfying this requirement, such means can be considered 
that these oscillators 1-1 . . . 1-12 are replaced by frequency dividers 
so that an oscillation frequency of a main oscillator may be 
frequency-divided. However, in this case, if the oscillator frequencies 
obtained at output terminals of these frequency dividers are those shown 
in FIG. 1, the oscillation frequency of the main oscillator becomes 268.08 
MHz by obtaining the greatest common measure of the frequency-dividing 
ratios of these frequency dividers. Frequency dividers for 
frequency-dividing such high frequencies as above are costly, and the main 
oscillator becomes also costly, and therefore these are not practical. An 
oscillation frequency of a main oscillator owned by a conventional 
electronic musical instrument such as an electronic organ or the like is 
2.0002 MHz at maximum. 
Accordingly, in the case where the present invention is built into a 
conventional electronic musical instrument, the oscillator provided 
therein cannot be utilized. 
A second embodiment shown in FIG. 2, is constructed to avoid this 
disadvantage. The input terminal A is connected to the respective 
frequency dividers 3-1 . . . 3-6 through a phase detector 20a, a lowpass 
filter 20b and a voltage controlled type oscillator 20c connected in 
series. An output terminal of the frequency divider for root 3-1 is 
connected to a feed-back signal input terminal 20a' of the phase detector 
20a, and thus a phase-locked loop (called hereafter PLL20) is formed by 
the combination of the phase detector 20a, the low-pass filter 20b, the 
voltage controlled type oscillator 20c and the frequency divider for root 
3-1. 
If, now, the input terminal A is applied with a signal of a frequency 2093 
Hz, this signal is phase-detected and a difference thereof from an input 
signal applied to the feedback signal input terminal 20a' is taken out as 
an output signal. A voltage signal is obtained therefrom through the 
filter 20b and causes the voltage controlled type oscillator 20c to 
oscillate. The oscillation frequency of the output thereof is applied with 
and frequency-divided by the frequency dividers 3-1 . . . 3-6. An output 
signal of the frequency divider for root 3-1 is fed back to the feedback 
signal output terminal 20a'. Thus, the phase detector 20a generates a 
difference signal so that the two input signals may become equal to each 
other in frequency and cause oscillation of the voltage controlled type 
oscillator 20c. Thus, when the oscillation frequency of the oscillator 20c 
becomes 1059.1 KHz, the frequency divider for root 3-1 becomes 2093 Hz in 
its output frequency because the frequency-dividing ratio thereof is 506, 
so that, the difference between the two input frequencies of the phase 
detector 20a becomes zero, and thereby the PLL 20 is locked. Accordingly, 
the frequency 1059.1 KHz is applied to the respective frequency dividers 
3-1 . . . 3-6, so that there can be obtained at output terminals of these 
frequency dividers 3-1 . . . 3-6, signals of relations of root, minor 
third, major third, fifth, sixth and seventh in relation to the C tone. 
When a frequency 1976 Hz is applied to the input terminal A, and thereby 
the voltage controlled type oscillator 20c oscillates at a frequency 
999.856 KHz, an output of the frequency divider for root 3-1 becomes 1976 
Hz and the PLL 20 is locked. As a result, there can be obtained signals 
having relations of root, minor third, major third, fifth, sixth and 
seventh in relation to the B tone. 
Thus, by applying musical tone signals of respective tones C, B, . . . C, 
C# to the input terminal A there can be obtained at output terminals of 
the frequency dividers 3-1 . . . 3-6 signals having relations of root, 
minor third, major third, fifth, sixth and seventh in relation to 
respective tones. Thus, the input terminal A is diverged to form 
respective input terminals 22-1 . . . 22-12 led out through respective 
gate circuits 21-1 . . . 21-12, and these terminals 22-1 . . . 22-12 are 
connected to output terminals of respective oscillators provided in a 
conventional electronic musical instrument. Consequently, be properly 
closing switches such as key-switches 23-1 . . . 23-12, for instance, 
connected to control terminals of the gate circuits 21-1 . . . 21-12, the 
respective gate circuits 21-1 . . . 21-12 are correspondingly opened, 
whereby musical tone signals can be obtained having relations of root, 
minor third, major third, fifth, sixth and seventh in relation to the 
input signal. 
The musical tone signals thus obtained become musical tone signals in major 
or minor by the selective operation of the selection switch 4a as 
described above in connection with FIG. 1. 
Thus, according to the present invention, a musical tone signal is applied 
to a frequency divider for root, a frequency divider for minor third, a 
frequency divider for major third, and a frequency divider for fifth, or a 
frequency divider for seventh so as to be frequency-divided. Thereby, 
musical tone signals having relations of root, minor third, major third 
and fifth or seventh in relation to the applied input tone signal can be 
simultaneously obtained, so that the apparatus can be extremely simplified 
in circuit construction in comparison with the conventional apparatus. 
Musical tone signals in minor or major can be simply obtained by selecting 
either of the musical tone signal of minor third and the musical tone 
signal of major third. 
Without further analysis, the foregoing will so fully reveal the gist of 
the present invention that others can, by applying current knowledge, 
readily adapt it for various applications without omitting features that, 
from the standpoint of prior art, fairly constitute the essential 
characteristics of the generic or specific aspects of this invention, and 
therefore, such adaptations should and are intended to be comprehended 
within the meaning and range of equivalents of the following Claims.