Disclosed herein is an instance of a media modality controller of a communication system which is assigned to convey media modality control signals of a communication event to respective media modality agents of endpoints of the communication event without accessing respective call agents of the endpoints. The media modality controller instance is so assigned independently of a call controller of the communication system and responsive to an instruction received via the network. The media modality controller instance is released from said assignment responsive to the media modality controller instance returning a response to the received instruction while the call controller continues to operate in communication with the call agents of the endpoints.