Performance Factors in Control of High-Dimensional Spaces Guy E. Garnett Camille Goudeseune University of Illinois at Urbana-Champaign {garnett,cog} @uiuc.edu Keywords: cognition, perception, control, multidimensionality Abstract Our work on instrument design and instrumental performance interfaces has led us to consider in detail the mappings from the performer's gesture space to the listener's perceptual space. The performer's gesture space includes the performer's conceptualization of the instrumental interface, from their physical gestures to the connection of these gestures with the resultant sounds. Since high-quality performance requires tremendous control of sonic detail, we also need to consider the kinds of sounds that may result and the qualities of variability available in those sounds. We address each of these problems through new techniques for creating mappings between controllers and the sonic results. 1. Design Problems in Electronic Instrument Performance In this project we attempt to solve some of the major synthetic-instrument design problems not by proposing new physical interfaces or controllers, and not by creating new synthesis algorithms, but by improving tools for understanding and designing the mappings between the physical interfaces and the resultant sounds-regardless of which synthesis algorithms are used. The problems we consider are two of the major difficulties facing designers of new electronic instruments: one, the performer's conceptualization of the instrumental interface, broadly conceived as including everything from the performer's physical gestures to the connection of these gestures with the resultant sounds. Two, the kinds of sounds that may result and the qualities of variability available in those sounds. We address each of these problems through new techniques for creating mappings between controllers and the sonic results. The issues associated with the first problem are, first, how to take advantage of the many years of practice that allow the performer to think largely in terms of the sound to be produced, andr only secondarily, in particular when practicing or when playing a difficult passage, in terms of the instrument ("am I using enough bow pressure here to get the sound I want") or even in terms of their own body ("maybe I should lean into this note more"). A part of this is in retraining reflexes and motor controls to do the right gesture at the right time; we call this physical retraining. Problems associated with physical retraining can be minimized by retaining a physical interface that is functionally very similar to the practiced instrument, such as a keyboard controller for pianists and, in our case, a violin controller for violinists. However, there is a more substantial issue involved that has received less attention: how does the performer conceptualize the relationship between their physical gestures and the sonic results? This is where issues of consistency, continuity, and coherence come into play: does the instrument produce the same sound given the same gesture? Does a slight change in gesture result in a slight change in sound? And, finally, do the sounds and gestures relate in ways we are habituated to from the physics of the nonsynthetic world-such as having a larger gestural force result in louder sound. We refer to this as the cognitive retraining problem, because to solve it performers have to retrain how they conceive of the sounds being produced. The system we describe attempts to minimize the cognitive retraining by allowing the designer the designer to associate particular points in the control parameter space with particular sonic results; the designer can therefore choose a mapping that involves minimal reorientation for the performer. From this association of pairs of points, the system creates a mapping from the space of control parameters to the space of synthesis parameters; this mapping is consistent, continuous, and coherent (at least no less so than the underlying controllers and synthesis algorithms are). -268 - ICMC Proceedings 1999
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