Hi --
The short answer is "Yes, it's possible." I suggest studying the files in:
C:\Program Files (x86)\Yamaha\XGWorks\XGEditor"
Each instrument has TBL and INI files. The instrument must also have an entry in the xgeditor.ini file. Bill Gross produced a "patch" for the Tyros 3 (attached) and a similar patch for the S910.
Be prepared to do some detailed tedious work. Also, make a back-up copy of everything. I blew up XGWorks when modifying the xgeditor.ini file. (XGWorks would no longer launch.) I suggest extreme caution!
All the best and good luck -- pj
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