bvideo
Based on your answer in the other thread, it sounds like the audio has to be populated (bounced) into the aux track, not just echoed through it for these purposes. So no such thing as "virtual" audio...
Remember, you have to make a
clip an RFX. You can't make a track, the structure that holds the clip, an RFX. If there's no clip, there's no possibility to create an RFX from it.