It's NOT possible to get a stereo sample to sound as good 'in mono' as it did in stereo. You lose the spatial ambience that true stereo provides. In the case of Yamaha stereo samples which also utilize stereo 'effects', when mixed to MONO, these effects are completely canceled out, leaving only the (phase canceled) raw sample heard. Yuck! I returned to the music store and with the assistance of the pro audio mgr, we tried tweaking the Bose PAS EQ settings till the cows came home, but were still never able to achieve (even close to) the realistic sound quality of the stereo piano sample as when heard thru discreet left/right speakers. I admit that a single Bose PAS unit sounds downright EXCEPTIONAL for vocals, acoustic instruments, & for mono electronic keyboard samples, but not stereo. I cannot afford to compromise the sound quality of the acoustic piano. - Scott