The phonatory excitation signal is the acoustic signal that is generated at the glottis by the vibrating vocal folds and pulsatile airflow. A shaping function model is a nonlinear memoryless input-output characteristic that transforms a simple harmonic into the desired output. The model can be fitted linearly to observed or simulated template cycles. The instantaneous values of the excitation cycle centroid, amplitude as well as length, and the cues for phonatory identity are set via distinct parameters. The synthetic phonatory excitation signal is zero on average, as well as identically zero when the glottal airflow rate is constant.