The Stereo piano patches contain frequency shifts that sound great when reproduced through a true stereo system where those shifts are mixed "in the air" - BUT when attempting to sum those two channels to mono electrically, it introduces phase cancellations. Typically that will make for a sound we might describe as "THIN" and weak.

The only way to get the true stereo of the piano on the gig with what you are using would be to buy another Bose L setup and run L to one and R to the other. Yeah, I know...$$$


--Mac