This talk begins with basic notation of tones and leads into the need for tone to be represented as features. The features as it turns out do not exist on the same plane, but needs to be separated into register features and contour features. Over the decades, there has been a growing acceptance for Bao’s (1990) model of tone. Beyond reviewing the main ideas in the literature, this talk ends with a proposal that any model must also be brought to bear on the correlation between the voicing of a syllable onset and its tone register.