1AVCenter opens the Windows Audio Mixer for you to tune your audio capturing. Microsoft Windows has two types of mixer: reproduction and recording.
1AVCenter uses a recording line to capture and record audio.
You can set 1AVCenter to capture and record audio from the audio line that mixes all other audio lines, this mixed audio line is usually called 'Stereo Mix' or 'Record Master'. Some newer audio drivers may not have this audio line. See troubleshoot for more information.
If you set 1AVCenter to capture and record audio from the mixed audio line then you can use the reproduction mixer to join music and voice together, or make other audio combinations that you can use 1AVCenter to capture and record.