The objective of the article is to present a polynomial waveshaper model of the phonatory excitation signal, as well as investigate its bandwidth when the model is driven by frequency and amplitude-modulated simple harmonic functions. The purpose of the modulation of the driving harmonics is the simulation of a time-variable intonation and accentuation, as well as phonatory regimes that are not simply periodic. The results show that the upper bound of the bandwidth of the synthetic excitation is equal to the upper bound of the bandwidth of the driving functions multiplied by the order of the model plus one. The sampling frequency must be chosen accordingly to avoid aliasing. This result can be generalized to any polynomial shaping function model.