These are the Sysex codes for Start and Stop:
Start: F0 43 60 7A F7
Stop: F0 43 60 7D F7
Here are some other codes you might want to use:
Vocal Harmony on: F0 43 10 4C 04 00 0C 40 F7
Vocal Harmony off: F0 43 10 4C 04 00 0C 7F F7
GM on: F0 7E 7F 09 01 F7
XG System on: F0 43 10 4C 00 00 7E 00 F7
Regards, Richard