The Variator is a compositional assistance tool that allows users to quicklyproduce and experiment with variations on musical objects, such as chords,melodies, and chord progressions. The transformations performed by the Variatorcan range from standard counterpoint transformations (inversion, retrograde,transposition) to more complicated custom transformations, and the system isbuilt to encourage the writing of custom transformations.This paper explores the design decisions involved in creating a compositionalassistance tool, describes the Variator interface and a preliminary set ofimplemented transformation functions, analyzes the results of the evaluationsof a prototype system, and lays out future plans for expanding upon thatsystem, both as a stand-alone application and as the basis for an opensource/collaborative community where users can implement and share their owntransformation functions.