Piping audio from multiple webpages into a multichannel stream

I'm looking for a solution to take the HTML5 audio from multiple tabs in a browser (I don't care which browser) and mix them into 1 multichannel audio stream. For example a 5.1 channel stream Browser tab 'A' --> Stream 1 - Front Left Channel Browser tab 'B' --> Stream 1 - Front Right Channel Browser tab 'C' --> Stream 1 - Rear Left Channel .... In another area I intend to split the stream to listen to different channels separately, but at this point I'm just trying to create the audio stream. I've read documentation for ALSA and JACK and am having trouble trying to find this exact scenario.