Bass tone producing device for an electronic musical instrument

Claim 2

In a keyboard electronic musical instrument having pedal keys, a bass tone producing device comprising: a fundamental bass tone signal source for generating a fundamental bass tone signal having predetermined pitches; at least one harmonic bass tone signal source for generating signals of harmonic bass tones having pitches at least one octave higher than that of the fundamental bass tone represented by the signal generated by said fundamental bass tone signal source; normally nonconductive keyer circuits rendered conductive upon the depression of an associated one of said pedal keys to derive therethrough the respective bass tone signals from both said bass tone signal sources; signal composing means for mixing in a preset ratio both the bass tone signals obtained through said individual keyer circuits; a first tone coloring filter supplied with output mixed signals from said signal composing means having a relatively low peak frequency to form a first composite signal; a second tone coloring filter supplied with the harmonic bass tone signal obtained through the corresponding one of said keyer circuits and having a peak frequency higher than that of said first tone coloring filter to form a second composite signal; means for reversing the phase of said harmonic bass tone signal in said second composite signal relative to the phase of said harmonic bass tone signal in said first composite signal; and a final signal composing means for mixing the first and second composite signals in a predetermined ratio.

Claim 3

A bass tone producing device according to claim 1 wherein said harmonic bass tone signal source comprises two units for generating different harmonic bass tone signals, and there is further provided another signal composing means for mixing in a preset ratio two output signals from both said harmonic bass tone signal source units.

Claim 4

A bass tone producing device according to claim 1 wherein said fundamental and harmonic bass tone signal sources comprise a frequency divider chain comprised of a plurality of cascade-connected bistable multivibrators each including two transistors, and said keyer circuits comprise emitter follower circuits each including a transistor which has its base connected via a diode to the collector of one of the two transistors included in the corresponding one of said bistable multivibrators and its emitter connected via a resistor to a line which is connected to one of a pair of positive and negative power sources via a resistor and a normally open switch closed upon depression of a corresponding key on said pedal keyboard, said transistor having its collector connected to the other power source with a resistor network connected between the collector and emitter of said transistor.

Claim 5

A bass tone producing device according to claim 1 further including a trigger circuit wherein said fundamental and harmonic bass tone signal sources comprise a frequency divider chain comprised of a plurality of cascade-connected bistable multivibrators each including two transistors, and said keyer circuits comprise a first group of emitter follower circuits each including a transistor which has its base connected via a diode to the collector of one of the two transistors included in the corresponding one of said bistable multivibrators and its emitter connected via a resistor to a Line which is connected via a capacitor to one of a pair of positive and negative power sources, said transistor having its collector connected to the other power source and said line being connected via a resistor and a diode to the output terminal of said trigger circuit rendered conductive upon depression of one of said pedal keys and also connected via a series circuit of a diode and a resistor network to the other power source; and a second group of emitter follower circuits each including a transistor which has its base connected via a diode to the collector of the other transistor included in the corresponding one of said bistable multivibrators and its emitter connected via a resistor to another line which is connected via a capacitor to said one power source, said transistor having its collector connected to the other power source line and said line being connected via a resistor to the output terminal of said trigger circuit and also connected via a resistor network to the other power source.

Claim 6

A bass tone producing device according to claim 1 wherein said first tone coloring filter is a low pass filter.

Claim 7

A bass tone producing device according to claim 1 wherein said second tone coloring filter is a band pass filter.

Claim 8

A bass tone producing device according to claim 1 wherein said first signal composing means comprises a plurality of resistors connected at one end to the corresponding output terminals of said keyer circuits, said resistors being jointly connected at the other ends thereof.

Claim 9

A bass tone producing device according to claim 1 wherein said final signal composing means comprises two resistors connected at one end to the corresponding tone coloring filters, said resistors being jointly connected at the other ends thereof.

Claim 10

A bass tone producing device according to claim 4 wherein said trigger circuit includes a one-shot multivibrator.

Claim 11

A bass tone producing device according to claim 1 wherein said means for reversing the phase of said harmonic bass tone signal in said second composite signal comprises a phase inverter coupling the harmonic bass tone signal from said keyer circuits to said second tone coloring filter.

Claim 12

A bass tone producing device according to claim 1 wherein said means for reversing the phase of said harmonic bass tone signal in said second composite signal comprises means in said harmonic bass tone signal source for generating pairs of opposite phase harmonic bass tone signals, one of said bass tone signals being coupled to said first tone coloring filter, and the other of said bass tone signals, which is out of phase with respect to said one of said bass tone signals, being coupled to said second tone coloring filter.