Repetitive keyer actuating circuit for an electrical musical instrument

Claim 2

In an electrical musical instrument of the keyboard type having a plurality of selectively orperated keyswitches for connecting corresponding tone generator keyers to a source of keying voltage, a repetitive keyer actuating circuit operable in response to keyswitch actuation to produce electrical keying pulses for alternately and repeatedly actuating two sets of keyers, comprising: keying pulse generating means coupled between said source of keying voltage and said key-switches for alternately and repeatedly producing pulses on each of two output signal leads in response to actuation of at least one of said keyswitches; and a pair of sustain circuit means each coupled between an associated one of said output signal leads and an associated set of keyers for producing a keying pulse envelope having a multiple stage decay; whereby each set of keyers is actuated by an initially percussive and subsequently sustained keying pulse.

Claim 3

Apparatus as claimed in claim 1, wherein said pulse generating means comprises: switching circuit means coupled between said source of keying voltage and said keyswitches for producing a control signal in response to actuation of at least one keyswitch; oscillator circuit means for producing a repetitive series of pulses in response to said control signal; a bistable multivibrator circuit for producing alternating pulses on first and second output leads in response to said repetitive series of pulses; a control lead connected between said switching circuit means and said multivibrator circuit for setting said multivibrator into a preselected state upon initial appearance of said key-down signal; a first output circuit coupled between said first output lead and a first one of said sustain circuit means for operating said first set of keyers in response to a pulse on said first output lead, and including gating means coupled to said switching circuit means for initially operating said first set of keyers regardless of the initial state of said multivibrator circuit; and a second output circuit coupled between said second output lead and a second one of said sustain circuit means for operating said second set of keyers in response to a pulse on said second output lead.

Claim 4

Apparatus as claimed in claim 2, wherein said switching circuit means comprises: pulse generator circuit means for producing a pulse of predetermined duration and amplitude in response to actuation of at least one of said key switches; key-down detector circuit means for producing a key-down signal of amplitude substantially equal to said amplitude of said pulse in response to actuation of at least one of said keyswitches, said key-down signal having a parasitic component reflecting keyswitch bounce; and an OR gate coupled to said pulse generator circuit means and said key-down detector circuit means for producing said control signal in response to at least one of said pulse and said key-down signal; said duration of said pulse being greater than the key-bounce time, whereby said control voltage has no parasitic component due to key-bounce.

Claim 5

Apparatus as claimed in claim 2, wherein said oscillator circuit means comprises a unijunction transistor oscillator and a pulse amplifier coupled to the output of said oscillator.

Claim 6

Apparatus as claimed in claim 2, wherein said gating means comprises an OR gate.

Claim 7

In an electrical musical instrument of the keyboard type having a plurality of selectively operated keyswitches for connecting corresponding tone generator keyers to a source of keying voltage, switching circuit means for producing a control signal in response to keyswitch actuation comprising: pulse generator circuit means coupled between said source of keying voltage and said keyswitches for producing a pulse of predetermined duration and amplitude in response to actuation of at least one of said keyswitches; key-down detector circuit means coupled between said source of keying voltage and said keyswitches for producing a key-down signal of amplitude substantially equal to said amplitude of said pulse from said pulse generator circuit means in response to actuation of at least one of said keyswitches, said key-down signal having a parasitic component reflecting keyswitch bounce; and an OR gate having inputs coupled to said pulse generator circuit means and said key-down detector circuit means for producing said control signal in response to at least one of said pulse and said key-down signal; said duration of said pulse being greater than the key-bounce time, whereby said control voltage has no parasitic component due to key-bounce.

Claim 8

In an electrical musical instrument of the keyboard type having a plurality of selectively operated keyswitches for connecting corresponding tone generator keyers to a source of keying voltage, switching circuit means for producing a control signal in response to keyswitch actuation comprising: pulse generator circuit means coupled between said source of keying voltage and said keyswitches for producing a pulse of predetermined duration and amplitude in response to actuation of at least one of said keyswitches; key-down detector circuit means coupled between said source of keying voltage and said keyswitches for producing a key-down signal of amplitude substantially equal to said amplitude of said pulse from said pulse generator circuit means in response to actuation of at least one of said keyswitches, said key-down signal having a parasitic component reflecting keyswitch bounce; and an OR gate having inputs coupled to said pulse generator circuit means and said key-down detector circuit means for producing said control signal in response to at least one of said pulse and said key-down signal; said duration of said pulse being greater than the key-bounce time, whereby said control voltage has no parasitic component due to key-bounce.

Claim 9

In an electrical musical instrument of the keyboard type having a plurality of selectively operated keyswitches for connecting corresponding tone generator keyers to a source of keying voltage, a repetitive keyer actuating circuit operable in response to keyswitch actuation to produce electrical keying pulses for alternately and repeatedly actuating two sets of keyers comprising: switching circuit means coupled between said source of keying voltage and said keyswitches for producing a control signal in response to actuation of at least one keyswitch; oscillator circuit means for producing a repetitive series of pulses in response to said control signal; a bistable multivibrator circuit for producing alternating pulses on first and second output leads in response to said repetitive series of pulses; a control lead connected between said switching circuit means and said multivibrator circuit for setting said multivibrator into a preselected state upon initial appearance of said key-down signal; a first sustain circuit means coupled between said first output lead and an associated first set of keyers for producing a percussion-sustain keying signal to operate said first set of keyers in response to pulses on said first output lead; a second sustain circuit coupled between said first output lead and an associated second set of keyers for producing a percussion-sustain keying signal to operate said first set of keyers in response to pulses on said second output lead; and a gating means coupled between said switching circuit means and said first sustain circuit to cause operation of said first set of keyers upon initial keyswitch actuation regardless of the initial operating state of said multivibrator circuit.

Claim 10

In an electrical musical instrument of the keyboard type having a plurality of selectively operated keyswitches for connecting corresponding tone generator keyers to a source of keying voltage, a repetitive keyer actuating circuit operable in response to keyswitch actuation to produce electrical keying pulses for alternately and repeatedly actuating two sets of keyers comprising: switching circuit means coupled between said source of keying voltage and said keyswitches for producing a control signal in response to actuation of at least one keyswitch; oscillator circuit means for producing a repetitive series of pulses in response to said control signal; a bistable multivibrator circuit for producing alternating pulses on first and second output leads in response to said repetitive series of pulses; a control lead connected between said switching circuit means and said multivibrator circuit for setting said multivibrator into a preselected state upon initial appearance of said key-down signal; a first sustain circuit means coupled between said first output lead and an associated first set of keyers for producing a percussion-sustain keying signal to operate said first set of keyers in response to pulses on said first output lead; a second sustain circuit coupled between said first output lead and an associated second set of keyers for producing a percussion-sustain keying signal to operate said first set of keyers in response to pulses on said second output lead; and a gating means coupled between said switching circuit means and said first sustain circuit to cause operation of said first set of keyers upon initial keyswitch actuation regardless of the initial operating state of said multivibrator circuit.

Claim 11

Apparatus as claimed in claim 7, wherein said switching circuit means comprises: pulse generator circuit means for producing a pulse of predetermined duration and amplitude in response to actuation of at least one of said key switches; key-down detector circuit means for producing a key-down signal of amplitude substantially equal to said amplitude of said pulse in response to actuation of at least one of said keyswitches, said key-down signal having a parasitic component reflecting keyswitch bounce; and an OR gate coupled to said pulse generator circuit means and said key-down detector circuit means for producing said control signal in response to at least one of said pulse and said key-down signal; said duration of said pulse being greater than the key-bounce time, whereby said control voltage has no parasitic component due to key-bounce.

Claim 12

Apparatus as claimed in claim 7, wherein said oscillator circuit means comprises a unijunction transistor oscillator and a pulse amplifier coupled to the output of said oscillator.

Claim 13

Apparatus as claimed in claim 7, wherein said gating means comprises an OR gate.