Interaction with a machine is different in a vast number of ways from interacting with a person. For the most part such interactions must be treated separately and it is a positive characteristic that the person should be aware that they are interacting with a machine. Yet we pose the suggestion that human-machine interactions could be enhanced if the machine were endowed with the human-like trait of ‘liveness’ (derived from performance theory) while at the same time avoiding the hazard of Mori’s Uncanny Valley (derived from robotics). We report the results of a series of experiments in which we attempted to invest synthetic voices with this characteristic of liveness. These culminated in an evening of theatre performances in which human and synthetic voices were deliberately mixed and confounded. We come to the conclusion that liveness is possible to achieve in synthetic interactions and may be measurable. We suggest that other forms of interaction might be enhanced by the application of liveness.