You may wanna try this on a hunch here:

Biab will allow you to have 2 instances of the program open. Not sure how it works with Asio though or a DXi at the same time, worth a try. Open the 2nd one and select blank 4/4 style and loop it. See if it will allow you to play your keyboard through the 2nd one while practicing over the 1st open Biab program?

Trax