Editing Strategies for Bézier-Modeled Continuous Expression Curves

PICACS (Pitch Curve Analysis and Composition System) is a software prototype inspired in part by study of Indian classical music. The primary motivation of the system is to facilitate analysis, composition, and convincing computer rendering of music that is characterized by detailed, expressive shaping of the continuum between scale steps. The system creates models of pitch, amplitude, and spectral-centroid expression envelopes by utilizing nonlinear least-squares fitting of constrained Bézier spline curves. Details of the modeling system have been published elsewhere; this paper focuses on the unique challenges that arise in designing an editing system for such models to support compositional purposes. While some of the challenges are specific to the Bézier model, it is clear that many of the challenges would apply to any system that seeks to support modelling and editing of continuous expression using sets of linked curves and multiple layers of expression data.