How to merge two microphone inputs into a single virtual microphone in realtime?

Question

If I connect two microphones to my computer, how would I merge it in to a single virtual microphone. I want the person I am calling on Skype to hear both microphone inputs, preferably only using software.

Answer 1

https://askubuntu.com/questions/868817/collecting-and-mixing-sound-input-from-different-microphones, building on http://www.pclinuxos.com/forum/index.php/topic,119695.msg905379.html#msg905379 offers you an answer. It describes how to add fake channels - first one for collecting the inputs

  pactl load-module module-null-sink sink_name=inputs

and setting channels up for the diverse input

 pactl load-module module-loopback sink=inputs

enter the latter command once for each input; the command returns a number; the latter you need later.

the two links describe how to use pavucontrol to link these channels.

Answer 2

I'd look into alsa with the multi plugin. I've only tried it for playback, but if it doesn't handle capture, perhaps you'll find an analogue for capture.