This is probably a simple question. I'm new to the Yamaha MODX. I'm bringing up a performance. I'm adding a part to it. I then save it as a live set. My understanding which may be wrong, is the changes to that live set should be saved but if I go to another live set and back or turn the keyboard of and on, the saved live set reverts back to the default setting. In other words it drops the part I added. Is this correct?

What it does and how it behaves will depend your your instrument’s settings.

Most folks set their instruments so that when they STORE a Performance to the User Bank or when they register a Performance to a User LIVE SET slot, what they STORE and register to the Live Set area will remain in memory.

However, there are settings (typically only used when the MODX is on display at Trade Shows or in retail stores, where they would rather not leave the internal memory open to just anyone coming along to overwrite. To prevent changes they may set the instrument so that the internal data cannot be changed — it re-initializes itself when next you power up.

But YOU would have to make these changes to your instrument’s UTILITY settings:
Press [UTILITY] > touch “Settings” > “Advanced”

Init On Boot (Initialize User Data on Boot-up)
Determines whether the User Data is initialized (On) or not (Off) when the power of the instrument is turned on.
Settings: Off, On ______________

You want to have this set to OFF.

STORE and SAVE
If this is not the issue, then we have to look elsewhere for a cause of the behavior. For example, STORE is different from SAVE - if we are using the official terminology of your MODX. Short story: you must STORE a Performance, or Sequence before you register it in a User LIVE SET...

Notice I am using the word STORE, when you create a Performance you press the [STORE] button to write the Performance to an internal USER Bank location. If you started with a preset Performance or an Init Performance, when you press [STORE] you will given an option to NAME the Performance... do so and then tap ”Done”. If you are editing an already stored Performance you will be given an opportunity to overwrite the existing Performance or create a New Performance ( if New is selected, you are offered to reName it).

Notice I used the word “register” a Performance in a Live Set slot... only a properly STORED Performance
(Preset Performances, User Performances) can be registered to a Live Set slot. If the Performance is *Stored* to internal memory, it can be successfully registered in a User Live Set.

When you want to add the current Performance, current Pattern, current Pattern Chain, or current Song to one of 2048 USER “LIVE SET” slots, you do so by holding [SHIFT] + [LIVE SET] from the main screen of the Performance or Sequence you wish to associate with the slot.

You will be shown your Live Set area, with a white box framing an empty Live Set slot... you can place it here by tapping that flashing white box or you can replace an existing Live Set program by tapping any box you desire.

There are 8 Banks of 256 Live Set locations (that’s 2048 total)
User Bank = is shown top left.
Each “Live Set” User Bank 1-8, has 16 PAGES, Each PAGE has 16 slots.

You will know you have placed it in the Live Set when the white box stops flashing, the new Performance’s Name will appear in the box and the background of that box turns orange.

SAVE, by the way, is the MODX terminology for writing your MODX data to a USB Flash Stick plugged into the USB “To Device” port.
This operation can be used to Save the current User Bank to a File. Either a User File (.X8U) or as a Library File (.X8L) etc., etc. You are literally, Saving the Stored data to an external file.

STORE to internal memory.
SAVE to USB stick. (Only the *Stored* data gets Saved).

Thank you. The answer was I wasn't Storing the Performance before adding it to a live set. I also discovered the answer from this video link attached to this response.

Thanks again for your response.