Diachronic phenomena of voicing and devoicing are explained here as resulting from cumulative effects of phonetic tendencies and preferences underlying speech production and perception. Regular diachronic change in voicing, either inferred from dialectal variation or manifested in written records, is the equalized result of sociolinguistic tuning processes in the transmission of the phonetic habits and perceptual feedback control from one generation of speakers to the other. Since phonation is not an autonomous component of the speech production mechanism, but dependent on both initiation and articulation, fluctuation in the execution of the phonation gesture is inherent to speech and thus governed not only by segmental context, but also by prosody. From the dynamic interaction of phonation with initiation and articulation, tendencies of change can in principle be predicted, but only in terms of probability: the implementation of sound change in a given historical scenario largely remains a matter of reselection within the spectrum of realisational variants, related to sociolinguistic processes of levelling and/or segregation that are hardly recoverable from what is usually known about speech communities of the past. On the one hand, synchronic variation with respect to voicing, especially in obstruents, can persist for ages without causing any change in the phonological system of the respective language or dialect. On the other hand, obstruent systems can be rearranged quite radically (in the course of so-called sound shifts) due to processes triggered by the antagonism of supraglottal constriction and transglottal airflow. Subsequent phase displacement of the phonation gesture can restore this antagonism, so that the system never reaches a state of rest. Diachronic tendencies of voicing and devoicing reflect the inherent dynamics of speech production, often to the detriment of perceptual redundancy.