@Notex I downloaded VB Audio cable, which
- generates a new input device (pseudo-mic)
- generates a new output device (pseudo-speakers)
When I assign an application to use the new pseudo speakers, the sound is forwareded to the pseudo-mic.
Hitman doesn’t have this option, so I made the new output device the standard device on my system. This way, I can use Shadow Play to only record the mircophone, forwarded Hitman in this case, and NOT the regular audio.
To be able to hear Hitman, I had to forward the pseudo-mic sound to my regular (but not anymore standard) playback device.
I then muted all applications which use the standard device (this is the sad part of the workaround) or assigned their sound to the regular, not-standard playback device (an option which Firefox sadly lacks, for which I had to download an extra add-on).
I can draw the routing on a sketch if this is too confusing. Trying to do it yourself?