Non linear techniques are used more and more commonly in musical sound synthesis Waveshaping allows to produce periodic sounds, whose spectra depend on the input amplitude, but not on the input frequency, as the process is memory-less.This variation can be achieved only acting on the control parameters. When an automatic dependence is required, a non-linear transformation with memory has to be employed. An efficient method to realize it is presented in this work. The output signal is composed by the sum of some polynomial waveshapings, each applied to progressively delayedvalues of the input sinusoidal. The resulting static and dynamic spectra are deeply analyzed. Designing criteria and three different implementations are discussed both from a theoretical and a practical point of view.