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US 4,408,514 AGranted
Electronic musical instrument having portaments property
AssigneeNippon Gakki Seizo Kabushiki Kaisha
InventorHideo Suzuki
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AssigneeNippon Gakki Seizo Kabushiki Kaisha
InventorHideo Suzuki
Estimating the term…
In a electronic musical instrument wherein a portamento is played by supplying the pitch voltage corresponding to a subsequently depressed key to a capacitor holding the pitch voltage corresponding to a previously depressed key, the charge and discharge currents of the capacitor corresponding to the difference between the two pitch voltages are controlled to vary exponentially thus changing exponentially the capacitor terminal voltage. The terminal voltage of the capacitor is applied to drive a voltage controlled oscillator to vary its oscillation frequency. To vary exponentially the terminal voltage of the capacitor, a mutual conductance converter is connected between the capacitor and a keyboard section and the output current from the mutual conductance converter is controlled by a control signal corresponding to the terminal voltage of the capacitor.
In an electronic musical instrument including a capacitor which is charged with a pitch voltage to hold the same, and a voltage controlled type oscillator which is controlled by the terminal voltage of said capacitor for playing a portamento, the improvement which comprises a first mutual conductance converter responsive to an input voltage signal to produce a current signal for varying said capacitor terminal voltage, means for supplying the current signal of said mutual conductance converter to said capacitor, means for detecting said capacitor terminal voltage to produce a control voltage signal corresponding to said capacitor terminal voltage, means coupled to said mutual conductance converter and said detecting means for controlling the current signal of said mutual conductance converter in accordance with said control voltage signal so that said current signal is substantially directly proportional to said capacitor terminal voltage thereby causing said capacitor terminal voltage to vary exponentially with respect to time both in ascending and descending characteristics, and a comparator responsive to said pitch voltage and said capacitor terminal voltage for delivering to said mutual conductance converter an output voltage signal as said input voltage signal to said converter when said capacitor terminal voltage is in a predetermined relation in magnitude to said pitch voltage, said voltage controlled type oscillator having a substantially linear input-output characteristic thereby producing a tone signal having a frequency varying exponentially with respect to time in said both characteristics.
The electronic musical instrument according to claim 4 wherein said current signal control means is connected to supply to said mutual conductance converter a control current corresponding to the control voltage signal of said detecting means which is proportional to the terminal voltage of said capacitor.
The electronic musical instrument according to claim 5 wherein said current signal control means comprises a bipolar transistor with its base electrode supplied with a fixed bias potential, the emitter electrode supplied with the output control voltage signal from said detecting means, and the collector electrode connected to supply a collector current proportional to said control voltage signal to said mutual conductance converter.
Dependencies are inferred from the claim text.