This paper presents the timbre model, a signal model which has been built to better understand the relationship between the perception of timbre and the musical sounds most commonly associated with timbre. In addition, an extension to the timbre model incorporating expressions is introduced. The presented work therefore has relation to a large field of science, including auditory perception, signal processing, physical models and the acoustics of musical instruments, music expression, and other computer music research. The timbre model is based on a sinusoidal model, and it consists of a spectral envelope, frequencies, a temporal envelope and different irregularity parameters. The paper is divided into four parts: an overview of the research done on the perception of timbre, an overview of the signal processing aspects dealing with sinusoidal modeling, the timbre model, and an introduction of some expressive extensions to the timbre model.

This paper presents the research involved in the elaboration of the timbre model, a signal model which has been built to better understand the relationship between the perception of timbre and the musical sounds most commonly associated with timbre. The elaboration of the timbre model involves an overview of the related topics in many fields. In particular the signal processing, perceptual and physical considerations, which have been taken into account when elaborating the model, are detailed. This includes in particular the timbre perception research and results from physical models of musical instruments. The timbre model is based on a sinusoidal model, and it consists of a spectral envelope, frequencies, and a temporal envelope, which together form the deterministic part of the model, and different irregularity parameters, which form the stochastic part of the model. Many of the parameters of the model (the timbre attributes) are here associated with verbal opposition pairs, such as high-low and dark-bright. An overview is given of the relevant signal processing aspects, the perceptual and psycho-acoustic research with relevance, and the physical reality behind many of the choices made when elaborating the model. The analysis, estimation and understanding of the timbre attributes are related to relevant research, wherever applicable, giving indications on how to improve these issues, evaluate the improvement and relate the improvements to timbre perception. 1

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This paper presents a method for improving synthesis efficiency in sinusoidal models. In the case of synthesizing polyphonic music, many overtones can be pruned, using perceptual and trigonometric methods. The main contribution of this work is a pre-processing algorithm giving a significant reduction of the number of sinusoids to synthesize (from several thousands to around one hundred), consisting of an optimized masking and hearing threshold calculation, and a sinusoidal merging procedure for sinusoids close in frequency. The frequency difference that can be merged has been determined, and increased using analytic band limitation.

A real-time synthesis engine which models and predicts the timbre of acoustic instruments based on perceptual features extracted from an audio stream is presented. The thesis describes the modeling sequence including the analysis of natural sounds, the inference step that finds the mapping between control and output parameters, the timbre prediction step, and the sound synthesis. The system enables applications such as cross-synthesis, pitch shifting or compression of acoustic instruments, and timbre morphing between instrument families. It is fully implemented in the Max/MSP environment. The Perceptual Synthesis Engine was developed for the Hyperviolin as a novel, generic and perceptually meaningful synthesis technique for non-discretely