Graphic Waveshaping

Greenlee, Shawn

Proceedings of the International Conference on New Interfaces for Musical Expression

In the design of recent systems, I have advanced techniques that positiongraphic synthesis methods in the context of solo, improvisational performance.Here, the primary interfaces for musical action are prepared works on paper,scanned by digital video cameras which in turn pass image data on to softwarefor analysis and interpretation as sound synthesis and signal processingprocedures. The focus of this paper is on one of these techniques, a process Idescribe as graphic waveshaping. A discussion of graphic waveshaping in basicform and as utilized in my performance work, (title omitted), is offered. Inthe latter case, the performer’s objective is to guide the interpretation ofimages as sound, constantly tuning and retuning the conversion while selectingand scanning images from a large catalog. Due to the erratic nature of thesystem and the precondition that image to sound relationships are unfixed, theperformance situation is replete with the discovery of new sounds and thecircumstances that bring them into play. Graphic waveshaping may be understood as non-linear distortion synthesis withtime-varying transfer functions stemming from visual scan lines. As a form ofgraphic synthesis, visual images function as motivations for sound generation.There is a strategy applied for creating one out of the other. However, counterto compositionally oriented forms of graphic synthesis where one may assignimage characteristics to musical parameters such as pitches, durations,dynamics, etc., graphic waveshaping is foremost a processing technique, as itdistorts incoming signals according to graphically derived transfer functions.As such, it may also be understood as an audio effect; one that in myimplementations is particularly feedback dependent, oriented towards shapingthe erratic behavior of synthesis patches written in Max/MSP/Jitter. Used inthis manner, graphic waveshaping elicits an emergent system behaviorconditioned by visual features.