Abstract: A tone generating system for an organ comprises a first group of tone generators for producing notes of a first chromatic scale and second group of tone generators for producing notes of a second chromatic scale, slightly offset from the first. The tone generators are addressed via a microprocessor in response to keyboard input, wherein the fundamental and a first plurality of selected harmonic components of a given note are generated by respective tone generators of said first group, and the remaining harmonics are provided by generators of the second group. Harmonic amplitude coefficients for particular organ waveforms are stored in random access memory and are subject to change according to stop inputs coupled to the microprocessor.