ANGUS is a real-time voice transformation tool able to simulate cues of arousal/roughness on arbitrary voice signals with a high degree of realism. Vocal roughness is generated by highly unstable modes of vibration in the vocal folds and tract, which result in sub-harmonics and nonlinear components which are not present in standard phonation. We propose to simulate this physiological mechanism using multiple amplitude modulations driven by the fundamental frequency of the incoming sound.