An EDS modelling tool for tracking and modifying musical signals

When one intends to achieve a good sound quality in applying classical effects like time stretching or pitch shifting to a piano recording, the problem of separating the stable sinusoidal components from the mechanical noise has to be addressed. This decomposition allows for specific processing of each part. In the case of the piano, the effect must indeed be applied only on the sinusoidal part to preserve the naturalness of the sound, especially if the amount of the stretching or the shifting is large. In this paper, an adaptive parametric method is presented, based on an Exponentially Damped Sinusoidal (EDS) model for the signal. This technique is not limited by the well-known trade-off between the spectral resolution and the length of the analysis window as in classical Fourier based approaches (for instance the phase-vocoder). The signal subspace is directly tracked and the poles related to sinusoidal components are selected regarding the stability of their time trajectory. Some recent enhancements of the algorithms for audio signal processing are demonstrated; in order to achieve a lower complexity. The musical applications include modifications of piano sounds and the singing voice.