I have a Performance called Jump. Voice 1 is Pre 1 C8 from C-2 to G8.

I'm sure you mean PART 1 of the Performance is PRESET 1, C08 "Hard Chorus", is that correct?

It is difficult to figure which of the hundreds of parameters you have changed, we can only tell you where to start looking... there are several things that could be the cause. I'm thinking it would be a lot easier to simply to Initialize the Part and then reselect it.

Here's how:
From your Performance's main screen
Press [JOB]
Press [F1] INIT
Clear all the boxes EXCEPT "Part 1"

With only "Part 1" checked, press [ENTER]
This will clear whatever you did and insert Preset 1, A01 "Full Concert Grand"

Now just change it to "Hard Chorus" and redo any Edits, etc, you require.

Press [STORE] to update your Performance.
Hope that helps.

Bad Mister - Your directions worked, thanks. I have no idea what happened. Could you point me in the right direction in trying to find a human voice choir on my MOTIF? I have tried every voice that has the words choir or chorus in it and nothing sounds even close. Surely a machine as sophisticated as the MOTIF has such when the Korg Krome has a voice that even has a picture of a choir singing. Your thoughts are appreciated. Thanks, John R.

The Motif XF has many, many Libraries available. And unlike your initial problem which had to do with operating the Instrument (I could easily help you), picking sounds is really your responsibility. I have no idea what you are looking for... sorry.

Have you loaded any of the XF Libraries?