A conference server enables collaborative communications among a variety of client processes of varying configurations all operatively coupled over a computer network to each other and to the server. The server receives audio streams from participating client processes in a conference, selects which audio streams are active, and broadcasts one or more of the active audio streams to the client processes participating in the conference depending on the clients receiving capabilities and the conference parameters. The client processes receiving multiple active audio streams perform mixing locally at the client node. Without having to perform mixing at the server, resources are saved and the number of simultaneous participating client processes to the conference may be increased accordingly. The server is further capable of simultaneously accommodating multipoint clients and non-multipoint H.323 clients, as well as operating in multiway and "push to talk" modes.