Audio captureC++ 64-bit Visual Studio community 2017 project,
to capture in
stereo mix mode
any sound playing on a
multiplex audio card.

For the best audio quality, you must setup the record mode of the audio card in "
stereo mix", and disable the microphone.
More about this on this link
https://www.howtogeek.com/howto/39532/how-to-enable-stereo-mix-in-windows-7-to-record-audio/How to use AudioCap :1 - Start AudioCap.
2 - Start playing a movie (with a sound track) or a local or internet audio file (streaming).
3 - Press the [
Start capture] button, to see the oscilloscope PCM WIMDATA curve.
4 - Check "
Capture to Wave" if you want to create the "
capture.wav", or check "
Monitoring only" if you want to see only the
peak level.