I received lots of questions about the "XG-Lite" compatibility of the EXR-3 and EXR-5. And I couldn't give you the answer myself, so I asked Roland about it.
For example, what are the "542 XG Sounds" that are mentioned in the specs? Why can't I use them from the panel of the keyboard?
The answer was simple: "There are no hidden sounds inside the EXR-series. Since GS/GM uses different patchnumbers to locate sounds than the XG-standard, the EXR-series is capable of playing back Midi-files that were made for XG-keyboards.
In other words: The EXR-5 'knows' the soundtable of the XG-standard, and therefor you can use XG-midifiles on the EXR-5. Strings will be played as strings, even though the XG-standard uses a different patchnumber for it than the GS/GM standard. The EXR uses its own Roland-sounds to playback XG-songs. Since XG-standards also include several editing possibilities that the EXR does not have, it's called 'XG-Lite' compatibility".
Bummer? Hm. Not really. Not for me, anyway. The EXR-5 is so loaded with sounds that I think I have more than enough choices. Even after using the board for a couple of weeks now, I still need the soundchart to find the sound I'm looking for :-)
------------------Roland EXR-5 user