Electronic musical instrument having automatic bass tone selector

Claim 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.