I have stored a Midi File as a SONG ON Motif ES6 and then saved it on my USB THUMB DRIVE. So far so good. 

When I open the MIDI FILE I edit, delete some of the Instruments /THEN ATTEMPT TO SAVE the changes that I have executed on the MIDI File I also save as the MIDI FILE with a different file name on the USB thumb drive.

The changes are not saved? What am I doing wrong?

Thanks for your Time
Audiomatrix

Are you changing or deleting the VOICES and MIX you used in the MIDI file?
Sounds like that’s what you referred to.

If that is the case, changes in your song mix (added or deleted voices, edits to voices themselves, levels, pan, etc.) do NOT get
stored as part of the MIDI file. Those are changes that you must -
a) STORE to your Mix BEFORE you exit the song.
b) SAVE as an ALL file or SONG file to USB media.

You could also save your mix data (voices, pan, volumes, effects, etc.) in MIDI if you perform Mixing / Job / Bulk Dump command. Than, all mix settings will be saved as MIDI system commands (SYSEX) in one MIDI track. If you save such a MIDI file, your mix data will be preserved. But, you should at first check wheter you disabled Receive Bulk Dump or not
(Utility mode /[F5] MIDI / [SF2] SWITCH / RcvBulk).

Alex