Abstract: This invention relates to a system and method for altering the harmonic referent of segments of a music composition while maintaining the register of the musical segments and their conformity to a harmonic rule-base. By combining the three novel notions of a "role-preserving" transformation "shape-preserving" transformation, and a "register" preserving transformation, a novel operation enabled by the present invention can be described. Essentially, the invention allows a pitch to be moved from one harmonic context to another. The pitches are then constrained to take on values that have the same harmonic function as their corresponding original pitches, while remaining, as much as possible, within the same register as their corresponding original pitches. Secondly, when a group of pitches are moved together as a melody, the operation can preserve not only the function and register of the pitches but the shape of the melody.