Well, you could do it, but not in realtime, at the same time.

You could record one manual to the Melody track and the other to the Soloist track, one at a time. At playback, nobody but you would know.

Or--

You could do it rather easily in RealBand, with one manual on one channel and the second manual on another MIDI channel.

Maybe start in BIAB to get the song sketched out, then export and open in RealBand to add the two keyboard parts.


--Mac