I probably didn't explain it particularly well, but essentially it can have 2 audio inputs, so one being USB/3.5mm and another from onboard audio, and then mixes it to 1 for me to hear through my headphones. The PC however detects these two audio outputs and so I can set, and record, from the USB/3.5mm and on board audio independently. Its more joining two outputs I guess, rather than splitting the sounds.