This morning I re-installed the driver from Realtek. It actually came out a little different, and something called "Stereo Mix" actually appears as an option. However, it does nothing for me. It still will not send the sound that the system is playing (such as a music file) to my software.
At least I reclaimed my ability to get input from my pre-amp, however now it seems I must restart my own software with the input selection already made; if I change the selection in the middle of a run it doesn't feed that change to the software, have to close and reopen the program. Hassle but somewhat doable. But still cannot access sound that the computer is playing.
What is the software I am using, do you mean the program I wrote that I am analyzing the input with? I will tell you just a bit.
but to learn about it you can read this page of the tutorial, watch a video of it in action.
There are a lot of other pages but they are just subsidiary to this.
I looked at my code, it's been some years... I use the CALLBACK_EVENT mode in waveInOpen. Anyway, I think whatever method of WaveIn used just gets what the system supplies, which should be determined by the Recording control. But that is so very different in W10 from the Recording Control windows seen in W98 up to XP (which I still run).
I'm sure it will never work unless I dissect code, such as from OBS Studio, and write my own. And I'm determined to stay retired from getting that kind of headache.