Part of this work is focused upon the principle of engaging participants in an active, kinetic relationship with the musical process--be it with composition, interpretation, improvisation, or some new experience which can only exist with the aid of a computer. Though great technological advances have been made in music for sound production, processing, and compositional aids, these tools have far outpaced our ability to control them in musically interesting ways. Musical interfaces, whether for experts or novices, must possess a refined physical control and an intuitive link with the sounds they produce. A keyboard key which produces a giant electronic gong will not "play" as well as an instrument which requires a swing of the arm to produce the same sound. Moreover, as the musical elements we choose to offer for users' real-time control become more abstract -- concepts such as tempo, embellishment, or rhythmic activity -- the question of interface becomes even more challenging.