Recording individual application audio in Windows

I'd like to record audio from all open Windows applications (ie the ones present in the Volume Mixer) and simultaneously store them into multiple files. I'd also like to find the names of these audio outputs. Storing this audio before the sound levels have been changed with the volume slider would also be useful.

Is there a way to do this, and what would it require? Would it require use of winapi, an external library, or something more advanced?

I'm not looking for code or a pre-built solution: This is more of a learning exercise for myself. Thanks.