Recording music played by a different Windows application

Windows 8.1
Audacity 2.1.3

How do I record sounds being played by a different Windows application? The instructions I have for this say:

  • Run Audacity
  • Make sure the Input Device is set to Stereo Mix (SoundMAX Integrated Sound System)
    I don’t have SoundMAX Integrated Sound System on this PC, and I could not find it in a web search.
    How do I connect the sound output of the PC to the input of Audacity, so that I can record? I suppose what I want is some sort of software loop-back. I really don’t want a “real cable” loop-back.

Thanks - Rowan

Stereo Mix was commonly available on older machines. There is a revised technique published.

Computers don’t naturally want to do this because of the risk of distortion and feedback and the fact that there is no natural sound pathway that runs both directions at once. There is an addition problem that you can’t “steer” the connection, so what you get is everything on the machine, not just the work you want. It’s not unusual to discover the dog barking in your recording because the built-in microphone also went live.