To use the QY100 with other things via MIDI:
From the Pattern or Song modes press Menu.
Select Utility
Press Menu again
Select MIDI
Set things as you wish with the arrow and yes and no buttons:
MIDI SYNC: Set to External to sync to external MIDI clock. You have to put it back to Internal if you want to use it on its own.
MIDI CONTROL: Set to In, Out, or In/Out to send and receive MIDI data.
ECHO BACK: Set to Thru to make the MIDI Out port to be a MIDI through port. Set it to RecMontr if you want to filter out particular MIDI messages.
LOCAL ON/OFF: Set to Off if you want to disable the keyboard.
MIDI FILTER: You can disable one specific type of event at a time (I've never used this):
PB: pitch bend
CC: control change
AT: after-touch
Exc: system-exclusive
PATT OUT CH: Sets whether patterns are sent out in the first or second bunch of 8 MIDI channels.
XG PARM OUT: Sets whether the extra XG info. is sent out.
Press MENU again
Select FingeredZone
Specify which MIDI channel you want to receive data on, or All.
※ For more detail check the manual (linked at the bottom of this page).
※ I haven't tested sending and receiving data using the bulk dump feature.
When I've played regular General MIDI files from my computer through the QY100 they've sounded off, but stuff made for Yamaha's XG MIDI spec have been fine. I'm pretty sure it should be fine with regular GM I'm just missing a compatibility setting somewhere.