Programmable current source for filter or oscillator
AssigneeNorlin Industries, Inc.
InventorGlenn Gross
Life of this patent
Estimating the term…
Abstract
In order to tune the frequency characteristics of a filter or oscillator as an exponential function of the position of a note on a musical scale, a pulse stream with an exponentially scaled duty cycle is used to gate an on-off switch which controls an electronic tuning signal for the first or second stage of the filter or oscillator. The pulse stream source can be a pulse code generator responsive to a priority note generator, or it can be an oscillator-driven one-shot with an exponentially scaled power supply governing the charging rate of a reactive component which determines the one-shot cycle time. There are also pitch offset and pitch modulation features in the circuit, the latter being usable in a constant deviation or a constant interval mode.
Claims23
An electronic music circuit comprising:
- means for selecting a note on a musical scale;
- means responsive to said musical note selection means to produce a musical tone signal at the frequency of the note selected thereby;
- at least one frequency-dependent circuit having an input connected to receive said musical tone signal and a separate frequency response control input, the frequency response of said frequency-dependent circuit varying as a substantially linear function of a current delivered to said frequency response control input;
- an on-off switch having a signal input, a signal output, and an on-off control;
- means for delivering to said signal input of said on-off switch an unchopped tuning signal which is separate from said musical tone signal;
- a pulse source responsive to said musical note selection means to generate a series of control pulses having a duty cycle which is an exponential function of the musical scale position of said selected musical note, and connected to apply said control pulses to said on-off switch control so as to turn said switch on during each control pulse and off between control pulses for chopping said tuning signal at an exponential rate;
- and
- means responsive to said signal output of said on-off switch to deliver to said frequency response control input a current proportional to the duty cycle of said chopped tuning signal, whereby the frequency response of said frequency-dependent circuit varies as an exponential function of the unchopped tuning signal.
In an electronic musical instrument having means for selecting a note on a musical scale, and at least one frequency-dependent circuit having at least one stage, the frequency response of said circuit being tunable as a substantially linear function of a tuning signal current;
- an exponential tuning signal conversion circuit comprising:
- an on-off switch having a signal input, a signal output, and an on-off control;
- circuit means providing a tuning drive signal;
- a source providing control pulses having a duty cycle exponentially related to the position of said selected note on said musical scale;
- means coupling said switch signal input to said tuning drive signal;
- means coupling said switch signal output to at least one stage of said frequency-dependent circuit whereby to control the tuning thereof;
- and
- means coupling said switch on-off control to turn said switch on and off in response to said pulse source whereby said exponential pulse duty cycle causes said frequency response of said frequency-dependent circuit to vary as an exponential function of said musical scale position of said selected note;
- said frequency-dependent circuit being an oscillator employed as a musical tone generator, the operating frequency of said oscillator being tunable in response to said tuning drive signal.
In an electronic musical instrument having means for selecting a note on a musical scale, and at least one frequency-dependent circuit having at least one stage, the frequency response of said circuit being tunable as a substantially linear function of a tuning signal current;
- an exponential tuning signal conversion circuit comprising:
- an on-off switch having a signal input, a signal output, and an on-off control;
- circuit means providing a tuning drive signal;
- a source providing control pulses having a duty cycle exponentially related to the position of said selected noted on said musical scale;
- means coupling said switch signal input to said tuning drive signal;
- means coupling said switch signal output to at least one stage of said frequency-dependent circuit whereby to control the tuning thereof;
- and
- means coupling said switch on-off control to turn said switch on and off in response to said pulse source whereby said exponential pulse duty cycle causes said frequency response of said frequency-dependent circuit to vary as an exponential function of said musical scale position of said selected note;
- said tuning drive signal circuit means comprising;
- summing means having at least two inputs;
- and a multiplier responsive to an output from said summing means.
In an electronic musical instrument having means for selecting a note on a musical scale, and at least one frequency-dependent circuit having at least one stage, the frequency response of said circuit being tunable as a substantially linear function of a tuning signal current;
- an exponential tuning signal conversion circuit comprising:
- an on-off switch having a signal input, a signal output, and an on-off control;
- circuit means providing a tuning drive signal;
- a source providing control pulses having a duty cycle exponentially related to the position of said selected note on said musical scale;
- means coupling said switch signal input to said tuning drive signal;
- means coupling said switch signal ouput to at least one stage of said frequency-dependent circuit whereby to control the tuning thereof;
- and
- means coupling said switch on-off control to turn said switch on and off in response to said pulse source whereby said exponential pulse duty cycle causes said frequency response of said frequency-dependent circuit to vary as an exponential function of said musical scale position of said selected note;
- said frequency-dependent circuit comprising a first stage and a second stage, said first stage receiving said tuning drive signal and coupling it to said switch input, and said means for coupling said switch output to control the tuning of said frequency-dependent circuit comprises said second stage of said frequency-dependent circuit.
In an electronic musical instrument having means for selecting a note on a musical scale, and at least one frequency-dependent circuit having at least one stage, the frequency response of said circuit being tunable as a substantially linear function of a tuning signal current;
- and exponential tuning signal conversion circuit comprising:
- an on-off switch having a signal input, a signal output, and an on-off control;
- circuit means providing a tuning drive signal;
- a source providing control pulses having a duty cycle exponentially related to the position of said selected note on said musical scale;
- means coupling said switch signal input to said tuning drive signal;
- means coupling said switch signal output to at least one stage of said frequency-dependent circuit whereby to control the tuning thereof;
- and
- means coupling said switch on-off control to turn said switch on and off in response to said pulse source whereby said exponential pulse duty cycle causes said frequency response of said frequency-dependent circuit to vary as an exponential function of said musical scale position of said selected note;
- said switch comprising a transistor, the collector of said transistor comprising the switch output coupled to control the tuning of said frequency-dependent circuit, the emitter of said transistor comprising said switch input, the base of said transistor comprising said switch on-off control, and a voltage divider being coupled to said transistor base to bias it to an operating point representing an initial offset signal for controlling the frequency response of said frequency-dependent circuit.
In an electronic music circuit of the type having means for selecting a note on a musical scale, means responsive to said musical note selection means to produce a musical tone signal at the frequency of the note selected thereby, at least one frequency-dependent circuit having an input connected to receive said musical tone signal, the frequency response of said frequency-dependent circuit with respect to the frequency of said musical tone signal varying as a substantially linear function of said musical tone signal current, means responsive to said musical tone signal to provide a signal which is a function of said musical tone signal, an on-off switch connected in series with said functionally related signal and having an on-off control, and a source responsive to said musical note selection means for applying to said on-off control of said switch a series of pulses the duty cycle of which is exponentially related to the musical scale position of said selected note whereby said musical tone signal current is chopped by said on-off switch to control the frequency response of said frequency-dependent circuit as an exponential function of said musical scale position;
- the improvement wherein:
- said frequency-dependent circuit includes an amplifier stage with a gain control input, the frequency response of said frequency-dependent circuit being a function of the gain of said amplifier stage as well as of the musical tone signal current;
- and
- means for applying an additional signal to said gain control input of said amplifier whereby to further alter said frequency response characteristic.
In an electronic music circuit of the type having means for selecting a note on a musical scale, means responsive to said musical note selection means to produce a musical tone signal at the frequency of the note selected thereby, at least one frequency-dependent circuit having an input connected to receive said musical tone signal, means including an on-off switch having an on-off control input and arranged to alter the frequency response of said frequency-dependent circuit as a function of the duty cycle of said switch, and a source responsive to said musical note selection means for applying to said on-off control of said switch a series of pulses the duty cycle of which is exponentially related to the musical scale position of said selected note, whereby to control the frequency response of said frequency-dependent circuit as an exponential function of said musical scale position;
- the improvement wherein said pulse source comprises:
- a clock which operates at a fixed high frequency, means responsive to said musical note selecting means to represent said selected musical note in digital code form, means responsive to said digital code note representation for digitally processing the output of said clock to produce a stream of pulses the duty cycle of which is an exponential function of said musical scale position of said selected note, and means coupling said pulse stream to said on-off control of said switch.
Dependencies are inferred from the claim text.