Disklavier

Hi all,

I own a MPX1Z MarkIIXG silent system upright disklavier (with DKC500RW
control unit). Is it possible to have the internal silent system piano
sound (NOT the XG piano sound) playing at the same time as the acoustic
piano?

Also, how easy is it to add an external XG tone generator for the XG parts
on a Pianosoft Plus / midi arrangement, but have the silent system piano
sound coming through? The DB51XG board sounds rather dated compared to
even the bottom end of Yamaha's home keyboards at the moment - I'd like to
add some sparkle :)

Apologies in advance if these are overed in the manuals - I'm in the
process of clearing out ready to move and have started packing things away
ready.

Thanks,

James