Abstract: A special effects circuit for use in an electronic musical instrument, preferably an electronic organ, including a filter circuit having variable bandpass characteristics and a tone source supplying a signal to the input of the filter circuit. The bandpass characteristics of the filter circuit are modified in accordance with a control signal. Upon the occurrence of an input signal, a control circuit provides the filter circuit with the control signal at a random or pseudo-random value. The instrument player may select the source of input signals from a variety of sources within the organ thereby determining the times or frequency at which the control signal changes but the value of the control signal is random or pseudo-random. The tone signal output from the filter circuit has randomly or pseudo-randomly attenuated frequency characteristics and is coupled to standard organ output circuits for audio presentation.

Abstract: A voltage controlled filter with a plurality of cascaded phase shift circuit stages in a negative feedback path of an amplifier. Each phase shift circuit stage is a RC phase shift network which includes a series capacitor and a field effect transistor (FET) with its source-drain circuit connected as a shunt to ground. The magnitude of the effective source-drain resistance of the FET in each stage is controlled by a DC control voltage which is applied in common to the gate of each FET.

Abstract: An automatic rhythm programmer for an electrical musical instrument which provides electrical pulses for actuating musical voice generators according to predetermined rhythmic patterns, having provision for introducing any one of several predetermined variations into any basic rhythmic pattern and for automatically changing from one variation to another at a preselected rate. The programmer comprises a master oscillator, a first counter and an electronic commutator which periodically pulse in sequence a series of address lines in an integrated circuit read-only memory, which also contains a separate series of tracks for each basic rhythmic pattern, each track being in circuit with certain of the address lines and energized at predetermined times therefrom, each track also being connected to certain of the voice generators and operable to provide actuating pulses thereto.