Bob -- I looked in the User Guide for a short while, and then opted for an easy fix: hardware!

I just took the output from Behringer audio interface, and routed it to input channels on my little Yamaha mixer, which happens to have reverb as an FX. I then plugged my mike and headphones into the mixer, and voila! With this approach, I can hear a smoothed out version of my own playing over a BiaB tune... without recording anything.

Who knows? Maybe someone will be helped by reading this thread some day. In any event, I appreciate your guidance.