Sinusoidal modeling and manipulation using lemur

Lemur is an application for sinusoidal timbre manipulation that is available to anyone with an Apple Macintosh computer. Lemur implements an extended McAulay-Quatieri (McAulay and Quatieri 1985, 1986) algorithm for sound analysis and synthesis, which is based on the work of Rob Maher and Tames Beauchamp (Maher 1989). The Lemur analysis consists of a series of short-time Fourier spectra, from which significant frequency components are selected. Similar components in successive spectra are linked to form time-varying partials, called tracks. The number of significant frequency components, and, thus, the number of tracks, may vary over the duration of a sound. Syn thesis is performed by a bank of oscillators, with each oscillator reproducing the frequency and amplitude trajectory of a single track. Phase accuracy is maintained using cubic phase (parabolic frequency) interpolation between spectra. The Lemur model allows for extensive sound modification via Lemur's built-in editing functions, or by using other customized editors to modify the intermediate analysis file before performing resynthesis. As the Lemur file format contains only amplitude, frequency, and linking information for each track, it is easy for users to write customized Lemur file editors. This article discusses the sinusoidal model as it is implemented in Lemur, and its application to timbre manipulation.