Abstract: A client-server-based communications system includes: a communications network; an audio user interface, coupled to the communications network, for receiving a user selection command; an interactive voice response (IVR) system, coupled to the communications network, for receiving the user selection command via the communications network and generating a flow request in response to the user selection command; a visual user interface, coupled to the communications network; and a synchronization system, coupled to the IVR system and the communications network, for generating flow control information to control the visual user interface and the IVR system in response to the flow request, thereby synchronizing audio contents played by the audio user interface and visual contents played by the visual user interface.