The sysex (for SYStem EXclusive), info are in the beginning of a track, to set GM and GS
mode are most often in track 6 and 11. This is the message sendt to keyboard during load
about what settings to use.
I'm not much into Vocalists yet, tried it a few times, but I think you can preset the
keyboard to not receive such data when load if you want to preserve your personal settings.

When use a midifile that are ready for a vocalist machine, averything should be ready set
to most optional voicing performance regarding that song, and as far as I know and what
I've read about it, it's track 5 that are used as standard.
In some of those files I can see no other music programmed,so I guess you can delete track
5 and resave as a new file and the vocalist info will not load? (In others I've seen there
often are choir as well.)
But again, I've probably much more to learn about this yet, than most other users.
GJ