I have an Ubuntu 16.04.3 LTS system with

* an ASUS Xonar DGX soundcard, and
* a generic USB sound card.

At our church, we want to be able to broadcast a service as well as record it as a WAV file. To accomplish this, I have the 3.5mm audio output cable from the sound board connected to a splitter, so that there are two cables to plug into the "Line In" connector on each soundcard.

Then, I use "arecord" to record the audio on one card, and "darkice" to create an MP3 stream on the other. 

Ideally, I'd like to be able to have one soundcard handle both the recording and streaming simultaneously. Is such a thing possible? Or am I stuck using two soundcards with two applications?