This paper addresses the problem of signal characterization in terms of sinusoidal and non-sinusoidal com-ponents. A first measure of sinusoidality is reviewed. Drawbacks of this sinusoidal estimator are investigated and solutions proposed. Estimation of sinusoidality on non-stationary signal is then made on apre-processed signal. A phase derived sinusoidality measure and the use of Re-estimated Spectra are introduced which allow deriving very precise and local characteristics. Finally, this characterization is used in anew synthesis scheme using Additive and PSOLA synthesis.