Abstract: A control circuit for shaded-pole motors used in an acoustic pulsato system for producing special musical effects. The system includes a horn-type loudspeaker connected to a shaded-pole motor and/or a drum-type loudspeaker connected to a shaded-pole motor. Each type of loudspeaker has a feedback circuit and a means for the operator to select the desired speed for the motor. The feedback circuit quickly adjusts the actual speed of the motor to correspond to the selected speed by controlling the amount of current or power supplied to the motor. The drum-type loudspeaker feedback circuit also includes a braking circuit to quickly stop the motor and the drum rotation to prevent unpleasant spurious signals which occur if the drum loudspeaker is permitted to coast to a stop on a slower speed.

Abstract: The present invention is a circuit for controlling the sampling of plurality of channels in an electronic organ having multiplexed keying. The channels having information signals at a particular time period is sensed and used to address a memory. The memory has stored a plurality of sequences of digital signals for controlling the multiplexing and demultiplexing operations of the organ. Only those channels containing information signals are sampled which accordingly increases the sampling rate which increases the frequency of the harmonic component of the square wave signals that can be passed by the system and the distortion caused by aliasing of harmonics is diminished.

Abstract: The present invention is a differential sampling circuit for improving the signal to noise ratio by eliminating d.c. level distortion in square wave signals used as components for forming a stairstep or bright wave signal in an electronic organ having multiplexed keying. The multiplexed drawbar signals for even footages at both sides of a sampling resistor are demultiplexed, applied to a sample and hold circuit and applied as inputs to a differential amplifier to cancel any fluctuations of the d.c. signal component.

Abstract: An electronic musical instrument having tone signal sources and keyers for the tone signal sources has a time division multiplexer for multiplexing the key-down information in groups such as for the upper manual, lower manual and pedals. The keyers are provided in divider keyer packages with drawbar, or harmonic content, information being synchronously multiplexed with the key-down information to a single set of keyers.

Abstract: A DC offset correction circuit for use in an electronic organ for eliminating audible noise or thump produced by an instantaneous DC level shift in the standard organ keyer circuit at both key depression and release. A standard keyer circuit is responsive to the depression of a key on the manual by the organist and provides a square or stairstep waveform output at a frequency representative of the note key depressed. Each keyer output waveform includes a positive or negative polarity instantaneous DC level shift at both key depression and release which when coupled through a capacitive output circuit, such as a filter, provides an undesirable audible thump. The DC offset correction circuit comprises a monitoring circuit which is responsive to both key depression and release and a detector circuit responsive to the monitoring circuit to provide a DC level signal output of opposite polarity to the instantaneous DC level shift in the keyer circuit.

Abstract: An AC keying transient is simulated in a DC keyed electronic musical instrument by gating a pseudorandom frequency noise source output to the audio output circuit of the instrument during a brief time interval initiated by a legato pulse. The level of the noise is randomly selected from a range of values of a triangular wave form. The amplitude range of the triangular wave form is determined for each keyboard manual by chopping the highest drawbar voltage setting with an approximately 20 percent to 80 percent duty cycle higher frequency rectangular wave pulse gated by a low frequency square wave. The variable duty cycle wave form serves as an amplitude control for all keyboards with an equal effect being provided by the individual drawbar voltage settings for each keyboard. The chopper output is filtered to remove the variable duty cycle pulses leaving the triangular wave form which is integrated from the 6.8 hz square wave signal.