In Windows you can't natively (for want of a better word) use more than one audio interface at a time.
The work around is using another layer of abstraction like Asio4All. It's not something i'd recommend using as it add latency.
If i want to record audio in Reaper from sounds sources not going through my Interface i change to WASAPI (i think - or one of the other settings - it's been a while). I have totalmix now with my RME interface so i can route using that - again i've not done it as i've not had any need. So if your interface has mixing software native to it, you might be able to do it that way. Best of
- This reply was modified 3 years ago by MBI (Ian).