In our research on musical timbre, we seek representations of the perceptual structure inherent in a set of sounds that have implications for expressive control over sounds in composition and performance. With digital analysis-based sound synthesis and experiments on tone quality perception, we obtain representations of the sounds that suggest ways to provide low dimensional control over their perceptually potent properties. Subjective judgments of perceptual contrast between sounds provide the basic input data to multidimensional scaling programs that produce geometric representations. In the spaces that result from the scaling programs the various tones are represented as points and a good statistical relationship is sought between the distances in the space and the contrast judgments between the corresponding tones. The spatial representation is given a psychoacoustical interpretation by relating its dimensions to the acoustical properties of the tones. Controls are then applied directly to these properties in synthesis. The control schemes to be described are for additional synthesis and allow for the manipulation of the evolving spectral energy distribution and various temporal features of the tones. Tests of the control schemes are carried out in musical contexts. Taped examples of various timbral manipulations will be provided. Particular emphasis will be given to the construction of melodic lines in which the timbre is manipulated on a note to note basis. Implications for the design of human control interfaces and software for real-time digital sound synthesizers will be discussed.
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