Abstract: An electronic organ includes a plurality of buffers for receiving solo keyswitch status information, accompaniment keyswitch status without octave information, and depressed keyswitch status from an arpeggio keyboard. A scan circuit and a microprocessor gate the buffers into an input memory which retains an image of the solo, accompaniment, and arpeggio keyboards. A control program, stored in ROM, is responsive to the input memory, shared registers, and harmony switches actuable in several modes, to produce one or plural harmony notes in either open or closed harmony, and to assign different note names to the actuated keyswitches on the arpeggio keyboard. The resulting harmony and arpeggio notes are stored in an output memory and are transferred to a transistor matrix which activates solo keyers to produce harmony and arpeggio notes with solo voicing. A rhythmic harmony modulator is actuable to modulate the harmony notes in a rhythmic pattern of individual and delayed beats.