Bernie,

The S910 will play all the GM, XG, GM2 and even the Roland voices along with it's own voices without any special changes or instructions being sent to the keyboard. This has been true for all of the Yamaha arrangers for at least as far back as the PSR-2000.

And - with your keyboard being connected via USB, you do not even need a MIDI connection because the keyboard can do it via the USB now - both for MIDI IN and OUT - BTW, you can also connect directly via that same USB cable to an iPad for MIDI.

Yamaha has come a very long way with the USB capabilities and the newer keyboards. The MOX even has in addition to the MIDI 2way, but two stereo channels via that same USB cable. This is awesome stuff.

Bill G