Just use morse code via ham radio in full-QSK mode (full break-in). Everybody can chime in at any time, in milliseconds.
:-)
I am not at that performance level yet because the experts go at a high speed but I've heard groups where it almost sounded like the inside of a beehive.
One of the worst developments in phones was when companies switched to internal VoIP over their usual LAN. I've had many cases where a guy had to whip out his cell phone and call again because his office phone became unintelligible. Or it was "Let me call you back from the stock room, they've still got a real phone-phone".