Based on this naudio tutorial, I'm aware that naudio has the ability to record audio output in Windows. The article also mentions that you can set naudio to only record audio mixed by naudio.
It seems to me as though the tools to accomplish application-specific recording are in there, but I can't put the pieces together. Thoughts?
As far as I am aware, it is not possible with WASAPI to record sound from a single application of your choosing. Windows 8 does give you the ability to enumerate through the streams and set their volumes, but I don't think you can capture them. At present NAudio's WasapiLoopbackCapture class can only be used to capture the combined output from all applications.
To record the audio you output yourself, have a look at the SavingWaveProvider example I discuss here on my blog.