US3697664A

US3697664A - Electronic musical instrument having automatic bass tone selector

Info

Publication number: US3697664A
Application number: US120651A
Authority: US
Inventors: Ryu Hiyama
Original assignee: Nippon Gakki Co Ltd
Current assignee: Nippon Gakki Co Ltd
Priority date: 1969-12-10
Filing date: 1971-03-03
Publication date: 1972-10-10
Anticipated expiration: 1989-10-10

Abstract

In an electronic musical instrument comprising an upper keyboard for a melody performance, a lower keyboard for a chord performance and a pedal keyboard for a bass performance there are provided a chord detector for detecting the type of a chord played on the lower keyboard upon depression of the keys thereof; a bass selector responsive to outputs from the chord detector for selectively coupling out from the tone generators bass tone signals corresponding to a note included in the chords played on the lower keyboard; and a gate circuit supplied with the bass tone signals from the bass selector and so designed as to be enabled by operation of one of the keys of the pedal keyboard. The pedal keyboard comprises only one or two keys for controlling one gate circuit supplied with one bass tone signal corresponding to the root note, or two gate circuits supplied respectively with one bass tone signal corresponding to the root note and fifth note included in the chord played on the lower keyboard.

Description

United States Patent m1 ,69 ,6 4 Hiyama [451 Oct. 10, 1972 [54] ELECTRONIC MUSICAL INSTRUMENT OTHER PUBLICATIONS HAVING AUTOMATIC BASS TONE SELECTOR Pages 191-193, from Introduction to Electronic Systems, Circuits, and Devices, D. O. Peder-son, .l. .l.

[72] Inventor: Ryu Hiyama, Hamamatsu, Japan a t"; whinnery McGraw Hm Book New or [73] Assignec: Nippon Gakki Seizo Kabushilti Kaisha, Hamamatsu, Japan Primary ExamineF-Lewis H. Myers Assistant ExaminerU. Weldon [22] Flled' March 1971 Attorney-Flynn & Frishauf [2]] Appl. No.: 120,651

[57] ABSTRACT 30 Foreign Appucation p -m Data In an electronic musical instrument comprising an upper keyboard for a melody performance, a lower Dec. 10, 1969 Japan ..44/116848 keyboard for a chord performance and a pedal DOC. l0, Japan for a bass performance there are provided a chord detector for detecting the type of a chord [52] US. Cl ..84/l.l7, 84/ L19 played on the lower keyboard upon depression of the [51] lnt.Cl ..Gl0h 3/06 keys thereof; a bass selector responsive to outputs [58] Field o f searcli 84/101,133, l. 2 4, l.g6 from the chord detector for selectively coupling out 307/253 from the tone generators bass tone signals corresponding to a note included in the chords played on the 5 References Cited lower keyboard; and a gate circuit supplied with the bass tone signals from the bass selector and so UNITED STATES PATENTS designed as to be enabled by operation of one of the I keys of the pedal keyboard. The pedal keyboard com- 2 11 prises only one or two keys for controlling one gate 1 s at a circuit supplied with one bass tone signal correspond- TCTIIICS X to the too note, or two g circuits pp 3476864 Munch l al "84,124 x respectively with one bass tone signal corresponding 3,535,972 [0/1970 Teramshi ..84/l.26 X to the root note and fif note included in the chord played on the lower keyboard.

1i l2 Figures ,5 T UPPER ONE KEYBOA

CQLORING RD FIgTER

3 ,7 1 5 16 TONE S LOWER TONE GENERATORS KEYBOARD COLOR'NG I FILTER 9 CHORD DETECTOR l 10 11 I TONE BASS GATE 1 s COLORING ELECTOR FILTER PEDAL KEY PATENIEBlJcI 10 m2 SHEET 1 OF 5 F I G. l /5 TONE {6 UPPER COLORING KEYBOARD FILTER j 5 6 1 7 1 1 3 z 2 TONE S LOWER TONE GENERATORS KEYBOARD ga -g2 AMP.

i CHORD d DETECTOR 12 4 1 10 TONE J BASS I -cO| OR|Ns SELECTOR 4 FILTER 4 I F G 2 PEDAL KEY -L i D1 R o r r 2 (c1 \P -P1 W1 k 5:22

0 [671 K x a P 3 m] A m] x 5X. E [D7] x A [a A I i 82 $8 \59 510 11 $12\ PAIENTEMBI 10ml 3.697664 SHEEI 2 BF 5 PATENTED B 10 I972 3.697.664

LOWER PEDAL [c] [F] [e71 c1 FIG.5C

BASS

PATENTED 3.697.664

SHEET l [1F 5 UPPER q TONE 55 KEYBOARD gf l-gg 3 8 TONE LOWER z r Rl NG A M p i N CHORD DETECTOR {10A 11 A BASS .GATE

QHFCTORI i TONE Q 13A COLORING- BASS GATE 7 FILTER SELECTOR n h @118 14B-U U-14A F I G 6 PEDAL KEYS T0 TONE COLORING FILTER FIG.7

PATENTEMBI 10 1972 3697.664

SHEETSUFS FIG.8A

[c] [F] [6 1 [g1 LOWER PEDAL FIG.8B

[c1 [F1 [6 1 [c LOWER j PEDAL L FIG.8C

[C] [F] [67] [C] ELECTRONIC MUSICAL INSTRUMENT HAVING AUTOMATIC BASS TONE SELECTOR The present invention relates to an electronic musical instrument and more particularly to improvements to facilitate a bass performance on the pedal keyboard.

With a conventional electronic organ having upper, lower and pedal keyboards, a melody performance is generally played by operation of the upper keyboard with the right hand, a chord performance by operation of the lower keyboard with the left hand, and a bass performance by operation of the pedal keyboard with the left foot. In this case, the left hand chord performance and the left foot bass performance are commonly conducted with a certain rhythmic pattern, like that of a march or waltz. However, the cord and bass performances with the left hand and left foot require considerable skill, because they have to be played in conjunction with the melody performance with the right hand. Particularly, a beginner finds it extremely difficult to carry out a rhythmic accompaniment of chord and bass exactly conforming with a melody performance. The chord performance is effected by depressing some of the keys of the lower keyboard at the same time as well as rhythmically, and the bass performance is carried out by selectively depressing one after another those of the thirteen pedal keys constituting a full octave which conform with the chord performance. Accordingly, the bass performance presents greater difficulties to the beginner than the chord performance.

It is, accordingly, the object of the present invention to provide an electronic musical instrument facilitating a bass performance.

The object of the present invention is attained in that there are provided a chord detector for detecting the type of chord played on the lower keyboard upon depression of the keys thereof; at least one bass selector for selectively coupling out from the tone generators bass tone signals corresponding to a note included in the chord in response to output signal from the chord detector; and at least one bass gate circuit for receiving the bass tone signal from the bass selector, the gate circuit being conducted (i.e., enabled) upon depression of one of the the keys of the pedal keyboard. In accordance with the present invention it is only required that the pedal keyboard be provided with one or two keys.

The present invention can be more fully understood from the following detailed description when taken in conjunction with the appended drawings, in which:

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

FIG. 2 is a circuit diagram of a chord detector shown in FIG. I;

FIG. 3 represents a bass selector circuit and gate circuit shown in FIG. I;

FIG. 4 illustrates a bass selector circuit and gate circuit according to another embodiment of the invention;

FIG. 5A, 5B and 5C show musical notations useful in explaining the operation of the electronic musical instrument of FIG. I;

FIG. 6 is a block diagram of an electronic musical instrument according to another embodiment of the invention;

FIG. 7 is a circuit diagram of the bass selectors of FIG. 6; and

FIG. 8 indicates musical notations useful in explaining the operation of the electronic musical instrument of FIG. 6.

Referring to FIG. 1, tone signals from tone generators I are distributed to the upper, lower and

pedal keyboard channels

2, 3 and 4. As is well known, the upper keyboard channel 2 includes an upper keyboard 5 having key switch circuits for selectively keying tone signals from the tone generators I upon depression of the keys and tone coloring filters 6 for converting the selected tone signals to musical tone signals. Similarly, the lower keyboard channel 3 includes a lower keyboard 7 having key switch circuits for selectively keying tone signals from the tone generators I upon depression of the keys and tone coloring filters 8 for converting the selected tone signals to musical tone signals.

According to the present invention, there is provided a chord detector 9 for detecting the type of chord played by operation of the lower keyboard 7. Further, the pedal keyboard channel 4 of the electronic musical instrument of the invention includes a bass selector 10 for selectively coupling out from the tone generators 1 bass tone signals corresponding to a note, preferably the root note included in the chords, in response to output signals from the chord detector 9; a bass gate cir' cuit II supplied with bass tone signals from the bass selector l0; and tone coloring filters l2 supplied with the bass tone signal upon conduction of the bass gate circuit 11. As illustrated in FIG. I, the bass gate circuit II is provided with a key switch I3 and is conducted (i.e., enabled) by a single key I4 constituting the pedal keyboard. Depression of the pedal key 14 actuates the key switch I3 to conduct the gate circuit 11, causing a bass tone signal to be supplied from the bass selector I0 to the tone coloring filters I2.

Musical tone signals from the

respective channels

2, 3 and 4 are amplified by an amplifier I5 and converted to audible sounds by a loud speaker 16.

With an electronic organ of FIG. 1, a melody perfonnance is conducted as usual by operation of the upper keyboard 5 with the right hand, and a chord performance by operation of the lower keyboard 7 with the left hand. While the chord performance is being played on the lower keyboard, the type of chord played is distinguished by the chord detector 9, and a bass tone signal corresponding to one of the notes included in the chord is selected by the bass selector [0 responsive to the output of the chord detector 9 and then supplied from the tone generators I to the gate circuit II. The rhythmic operation of the pedal key 14 causes bass tone signals to be supplied to the tone coloring filters 12 in a rhythm pattern corresponding to the operation of the pedal key 14. Namely, the present invention enables a bass performance to be carried out simply by operation of a single pedal key without the necessity of selecting one of a plurality of (thirteen) pedal keys as is the case with the prior art electronic organ.

There will now be described by reference to FIG. 2 the chord detector 9 of FIG. I. The chord detector 9 comprises a matrix circuit having a plurality of column lines, row lines and diodes positioned at the prescribed intersections of both lines. The matrix circuit has twelve column lines L, to L,, corresponding to the notes of one octave, the ends on one side of the column lines being grounded by normally open key switches S, to 8,, operated by the respective keys of the lower keyboard 7. The switches actuated by the keys corresponding to the same notes in the different octaves are respectively connected to the same common column lines included in the matrix circuit. The ends on the other side of the column lines are connected through a resistor R, to one end of a common power source 20, the other end of which is grounded. The matrix has the same number of row lines or

output lines

0,, 0,, 0,, as the kinds of chords to be played on the lower keyboard. FIG. 2 indicates seven row lines representing Chords L 11], I]. r-l. 1] and [8]. The ends on one side of the row lines are grounded through resistors R, and R, At the prescribed intersections between the row lines denoting these chords and column lines are connected diodes in the forward direction with respect to the polarity of the power source 20 to which the column lines are connected to detect. For example, for chord [C], there are connected diodes D of the indicated polarity to three intersections defined by row line 0, with column line L,, connected to switch S, operated by the key of the lower keyboard corresponding to note C included in chord [C], column line L, connected to switch 8,, corresponding to note E and column line L, connected to switch S, corresponding to note G.

Referring to the operation of the aforesaid chord detector, the diodes are connected to the intersections of the row lines and column lines in the forward direction with respect to the positive source voltage, so that the potential of the detection terminal of the row line, or the juncture between resistors R, and R, is normally kept positive. Depression of the keys of the lower keyboard corresponding to, for example, notes C, E and causes switches S,, S, and S, to be closed and in consequence column lines L,, L, and L, to be grounded. Accordingly, the power source 20 is shortcircuited with column lines L,, L, and L, by the resistor R,, preventing row line 0, connected to column lines L,, L, and L, by the diodes from being impressed with voltage, so that the potential of the detection terminal P, of row line 0,, that is, the voltage across the resistor R, is reduced to zero. At this time, the potentials ot'the detection terminals P,, P .of the other row lines are still kept positive. From the fact that the potential of the detection terminal of row line 0, associated with the chord [C] was changed from positive to zero, the chord performed by operation of the lower keyboard is distinguished as [C] The detected output controls the bass selector 10. This selector may be constructed as illustrated in FIG. 3.

FIG. 3 illustrates one of the selector circuits included in the bass selector l0 and a common bass gate circuit II, the selector circuit being associated with the chord [C ]v The selector circuit includes, for example, an NPN type transistor T, the collector of which is connected to a positive power source through a resistor 2!, the emitter of which is grounded through a capacitor 22 and the base of which is connected to the juncture between

resistors

23 and 24 which are disposed between the power source and earth. The base of the transistor T, lS normally supplied by the tone generators l with a bass tone signal C, corresponding to the root note C of the chord [C]. The emitter of transistor T, is connected to the output terminal P, included on the chord detector 9 for detection of the chord [C] shown in FIG. 2 through a diode 25 disposed in the same direction as the base-emitter diode of transistor T,. A bass tone signal from the selector circuit is drawn out from the collector of transistor T, through a coupling capacitor 26 and supplied to the bass gate circuit ll. Bass tone signals from the other selector circuits included in the bass selector 10 are also impressed on the same gate circuit ll through respective coupling EPEFlBP',

The bass gate circuit ll includes, for example, an NPN type transistor T,, the collector of which is connected to a power source (+V,) through a resistor 27, the base of which is connected to the juncture between resistors 28 and 29arranged in series between the power source and ground, and also to the capacitor 26 of the selector circuit, and the emitter of which is grounded through

resistors

30 and 3! and the key switch 13 of FIG. 1 in this order. The juncture between the

resistors

30 and 3| is connected to a control voltage source V, through a resistor 32, and a circuit including the resistor 3| and key switch l3 connected in series is shunted by a capacitor 33. The output from the gate circuit 11 is drawn out from the collector of the ansistor [:L'HQEEE a 2 294 There will now be described the operation of the circuit of FIG. 3. When the output terminal P, of an out put line 0, for detection of the chord [C] of FIG. 2 is supplied with positive voltage by the power source 20, the transistor T, is rendered inoperative to cease the supply of the bass tone signal C, to the bass gate circuit ll. When the chord [C] is played on the lower keyboard, namely when there are depressed the keys corresponding to the notes C, E and G, then the potential of the output terminal P, is reduced to zero as shown in FIG. 3 to cause the transistor T, to be rendered operative and the bass tone signal C, to be ipt ooresm The capacitor 33 connected to the emitter of transistor T, of the bass gate circuit It is charged by the voltage source (+V,, whose voltage is high enough to render the transistor T, normally nonconductive. When the key switch 13 is closed by operation of the pedal key 14, the charged voltage is dissipated through the resistor 31 and key switch 13 to decrease the emitter potential and in consequence render the transistor T, operative. Namely, when the key switch I3 is closed, a bass tone signal from the bass selector circuit T, which has already been energized is drawn out from the collector of transistor T, of the bass gate circuit II. The capacitor 22 connected to the emitter oftransistors T, of the selector circuit I0 is intended to allow the transistors T, to remain conductive for a predetermined length of time (preferably about 0.5 second), though, after the lower keyboard ceases to be operated, the voltage impressed on the output terminal P, of the chord detector 9 rises from zero to the same level as the source voltage.

The selector circuit including the transistor T, shown in FIG. 3 may be allowed to concurrently act as the gate circuit including the transistor T,. FIG. 4 illustrates such case. The same parts of FIG 4 as those of FIG. 3 and denoted by the same numerals. The juncture between the diode 25 connected to the emitter of transistors T, included in the bass selector circuit and the output tenninal P, of the chord detector 9 is connected to the control voltage source (+V,) through a circuit including a diode 3S and the normally closed key switch 13 connected in series. The diodes 35 is disposed in the forward direction with respect to the voltage source (+V,). The transistors T, of the other selector circuits are supplied with the control voltage through respective diodes 35, and common key switch 13.

In the circuit of FIG. 4, while the key switch 13 is closed, the transistor T, is rendered inoperative due to the control voltage V, though the potential of the output terminal P, of the chord detector 9 is made to otherwise become zero. Opening of the key switch 13 by depression of the pedal key 14 separates the emitter circuit of transistor T, from the control source and thus a bass tone signal can be derived from the collector of transistor T, as long as the potential of the output terminal P, of the chord detector 9 is zero.

There will now be described by reference to FIGS. 5A, 5B and 5C the operation of the electronic musical instrument of FIG. 1. FIG. 5A illustrates musical notations for the chord and bass performances which it is desired to play on the lower and pedal keyboards. It will be apparent from the illustration that the chords [C], [F], [6-,] and [C] are played in turn at the respective measures and that the bass performance is conducted by the root notes of the chords defined by the measures and that the bass performance is conducted by the root notes of the chords defined by the measures.

FIG. 58 indicates the manner of operation of the lower and pedal keyboards when the notations of FIG. 5A are to be played. As seen from the illustration, the lower keyboard should be rhythmically operated four times for each measure, whereas a single key constituting the pedal keyboard has only to be operated twice for each measure.

FIG. SC shows musical tones produced by the keyboard operation indicated in FIG. 58. It is seen that bass tones last longer than chord tones. This is due to the action of the capacitor 22 connected to the emitter of transistors T, included in the bass selector circuit as shown in FIGS. 3 and 4.

The foregoing embodiment relates to the case where the bass performance was carried out according to the root note on the chord alone, that is, only by operation of a single pedal key. However, the bass performance may also be conducted according to both the root and fifth notes of the chord and by operation of two pedal keys to provide a better musical effect. This embodiment is presented in FIG. 6.

According to the embodiment of FIG. 6, the pedal keyboard channel 4 includes a first bass selector 10A for selectively drawing out a bass tone signal corresponding to the root note of the chord; a second bass selector 103 for drawing out a bass tone signal corresponding to the fifth note of the chord; a first bass gate circuit IIA supplied with the bass tone signal by the first bass selector 10A; and a second bass gate circuit supplied with the bass tone signal from the second bass selector 10B. Output signals from the first and second bass gate circuits A and 11B are conducted to the common tone coloring filters 12. The pedal keyboard is comprised of two

keys

14A and 148. The key switches 13A and 13B actuated by the keys NA and 148 respectively are disposed in the first and second

bass gate circuits

11A and 118. FIG. 7 shows the circuits of the bass electors 10A and 10B of FIG. 6. These gate circuits 10A and 10B are of the same arrangement as that of FIG. 3 and the same parts of FIG. 7 as those of FIG. 3 are denoted by the same numerals. Elements included in the selector circuit of the root note are indicated by reference notations suffixed with the letter A and elements included in the selector circuit of the fifth note bear reference notations suffixed with the letter B.

In this case, the base of transistor T of the selector circuit 10A for the root note is supplied with a bass tone signal C, corresponding to the root note C of the chord [C]. And the the base of transistor T, of the selector circuit 103 for the fifth note is supplied with a bass tone signal G, corresponding to the fifth note G of the chord [C]. The emitters of transistors T,,, and T, are jointly connected to the output terminal P, of the chord detector 9 through diodes 25A and 25B respectively.

Outputs from the selector circuits of the root notes of the other chords are coupled to the gate circuit A. Similarly, outputs from the selector circuits of the fifth notes of the other chords are coupled to the gate circuit 1 1B. The circuit of FIG. 7 arranged as described above is operated in the same manner as that of FIG. 3. When the potential of the output terminal P, of the chord detector 9 decreases as shown in FIG. 7, the selector circuits T and T,,, are jointly rendered operative to cause has tone signals C, and G, to be drawn out therefrom and supplied to the

gate circuits

11A and 118. These circuits A and 11B are alternately conducted by either of the two

pedal keys

14A and 148.

FIG. 8A illustrates the musical notations of the chord and bass performances which it is desired to play by the electronic musical instrument of FIG. 6. It will be apparent from the illustration that the bass performance is carried out alternately according to either of the root and fifth notes of the chord. To this end, the two pedal keys have only to be operated alternately as shown in FIG. 88. Consequently, desired musical tones can be produced as shown in FIG. 8C.

The foregoing embodiments of FIGS. 3 and 7 relate to the cases where was conducted a bass performance according to the root note of one chord and the root and fifth notes thereof respectively. Where it is desired to carry out a bass performance by three or more bass tone signals with respect to one chord, namely, where, in case of, for example, the chord [C], it is desired to produce three bass tones corresponding to the root note C, fifth note G and other note E of the chord, it is only required to use one more bass selector circuit and one more gate circuit, and one more pedal key for control of the additional gate circuit.

What I claim is:

I. An electronic musical instrument comprising:

a plurality of tone generators;

an upper keyboard for melody performance having key switch circuits for selecting tone signals from said tone generators",

a lower keyboard for chord performance having key switch circuits for selecting tone signals from said tone generators;

a matrix-connected chord detector coupled to said lower keyboard for detecting and identifying the type of chords played on said lower keyboard by detecting which keys of said lower keyboard are actuated, said chord detector comprising:

a plurality of column lines, one end of each of which is grounded through a detector switch actuated through operation of said lower keyboard and the other end ofeach of which is connected to a DC. source through a resistor;

a plurality of row lines provided for each different chord and intersecting said plurality of column lines, said row lines being grounded at one end through a resistor; and

at least two diodes connected in the forward direction with respect to said D.C. source polarity between each row line and at least two of said plurality of column lines connected to said de tector switches operated by the keys of said lower keyboard actuated according to the chord, whereby upon operation of the keys of said keyboard to play a chord, those of said plurality of column lines which are connected to said detector switches actuated by the keys are grounded and said power source is also grounded through resistors connected to the column lines, causing said row line to be disconnected from said DC. power source and in consequence the voltage across said resistor connected to said row line to be varied, thus providing detection of the type of chord played;

at least one bass selector coupled to said chord detector and to said tone generators and responsive to the output of said chord detector for coupling out from said tone generators selected bass tone signals corresponding to one predetermined note included in said detector chords being played;

at least one gate circuit coupled to said bass selector for receiving said selected bass tone signals from said bass selector;

said has selector and gate circuit including:

a common transistor having an emitter, base and collector;

a first diode disposed in the forward direction with respect to the base-emitter diode junction of said common transistor and coupling said ate cir uit to c u le e selected bass tone s| nal feceived by sa|d gate lrcuit to an output terr inal to cause bass performance.

2. The electronic musical instrument according to claim 1 wherein said bass selector includes a plurality of selector circuits, each selector circuit being connected to receive a bass tone signal corresponding to the respective root notes of the chords played on said lower keyboard, said gate circuit being connected to said each selector circuit and said pedal keyboard is provided with a signal key and including means for selectively operating said gate circuit by its operation. single 3. The electronic musical instrument claim I wherein:

said bass selector comprises first and second selectors coupled to said tone generators, each selector including a plurality of selector circuits and each selector circuit of said first bass selector being responsive to said chord detector to couple out from said tone generators a bass tone signal corresponding to the respective root notes, and each selector circuit of said has selector being responsive to said chord detector to couple out from said tone generators a bass tone signal corresponding to the respective fifth notes of the chords played on said lower keyboard;

said gate circuit comprises first and second gate circuits, said first gate circuit being connected to said first bass selector and said second gate circuit being connected to said second bass selector; and said pedal keyboard is provided with at least two keys which include means for selectively operating said first and second gate circuits respectively. 0 t

according to

Claims

1. An electronic musical instrument comprising: a plurality of tone generators; an upper keyboard for melody performance having key switch circuits for selecting tone signals from said tone generators; a lower keyboard for chord performance having key switch circuits for selecting tone signals from said tone generators; a matrix-connected chord detector coupled to said lower keyboard for detecting and identifying the type of chords played on said lower keyboard by detecting which keys of said lower keyboard are actuated, said chord detector comprising: a plurality of column lines, one end of each of which is grounded through a detector switch actuated through operation of said lower keyboard and the other end of each of which is connected to a D.C. source through a resistor; a plurality of row lines provided for each different chord and intersecting said plurality of column lines, said row lines being grounded at one end through a resistor; and at least two diodes connected in the forward direction with respect to said D.C. source polarity between each row line and at least two of said plurality of column lines connected to said detector switches operated by the keys of said lower keyboard actuated according to the chord, whereby upon operation of the keys of said keyboard to play a chord, those of said plurality of column lines which are connected to said detector switches actuated by the keys are grounded and said power source is also grounded through resistors connected to the column lines, causing said row line to be disconnected from said D.C. power source and in consequence the voltage across said resistor connected to said row line to be varied, thus providing detection of the type of chord played; at least one bass selector coupled to said chord detector and to said tone generators and responsive to the output of said chord detector for coupling out from said tone generators selected bass tone signals corresponding to one predetermined note included in said detector chords being played; at least one gate circuit coupled to said bass selector for receiving said selected bass tone signals from said bass selector; said bass selector and gate circuit including: a common transistor having an emitter, base and collector; a first diode disposed in the forward direction with respect to the base-emitter diode junction of said common transistor and coupling said emitter to said chord detector; a capacitor coupling said emitter to ground; means coupling the juncture between said first diode and said chord detector to a control power source, said coupling means including a normally closed pedal switch opened by one pedal key and a second diode disposed in the forward direction with respect to said control power source; said base being connected to the corresponding one of said tone generators; and a coupling capacitor connected to said collector; and a pedal keyboard for bass performance provided with at least one key for selectively operating said gate circuit to couple the selected bass tone signals received by said gate circuit to an output terminal to cause bass performance.

2. The electronic musical instrument according to claim 1 wherein said bass selector includes a plurality of selector circuits, each selector circuit being connected to receive a bass tone signal corresponding to the respective root notes of the chords played on said lower keyboard, said gate circuit being connected to said each selector circuit and said pedal keyboard is provided with a signal key and including means for selectively operating said gate circuit by its operation. single

3. The electronic musical instrument according to claim 1 wherein: said bass selector comprises first and second selectors coupled to said tone generators, each selector including a plurality of selector circuits and each selector circuit of said first bass selector being responsive to said chord detector to couple out from said tone generators a bass tone signal corresponding to the respective root notes, and each selector circuit of said bass selector being responsive to said chord detector to couple out from said tone generators a bass tone signal corresponding to the respective fifth notes of the chords played on said lower keyboard; said gate circuit comprises first and second gate circuits, said first gate circuit being connected to said first bass selector and said second gate circuit being connected to said second bass selector; and said pedal keyboard is provided with at least two keys which include means for selectively operating said first and second gate circuits respectively.