How to set up a multi-party communicator, with a publisher and one subscriber active at a time, while remaining subscribers joining in as an audience?
OpenTok QA staff here,
It's fairly easy. Just create a session, and then, from the device you want to be the speaker, create the publisher and the subscriber. In the other devices, just create the subscribers, and subscribe to the session. You are not limited to one publisher/multiple subscribers. Each device can also publish audio and/or video to the same session, so that every participant and see/listen to each other.
You can find more information in the Tokbox Developer Center, for instance:
https://tokbox.com/developer/tutorials/ios/basic-video-chat/
I hope this helps.