Hi Zack,
Welcome to Yamaha Synth!

b) I am experiencing that in MS, I can send MSB/LSB to each channel to the Motif ES6 (Omni mode) and it will call up the correct voices. MultiTimbral tone module and keyboard controller at the same time! Very cool! MS at this point literally replaced my Motif ES6 Pattern Mode interface WHILE I maintain the Motif ES6 sound. However, the volume controls on the Motif seems global. Meaning, if i adjust the volume on say one of the channels in my split/layer setup (aka MS “Patch"), other the channels seems to adjust as well.

Ok, it could be the typos but I think I understand the question.

My questions for you are:
What and why do you mention (OMNI Mode) I assume you want the Motif ES in Pattern mode, where normally the ES is set to receive on 16 separately addressable MIDI channels for the Parts, 1-16. You can address the Master volume of the ES separately from the 16 independent internal PARTS. Those are separate parameters. There are 16 Part Volumes, and a separate master Volume.

The [UTILITY] mode parameter for Basic Receive Channel is for Voice and Performance modes only. In Song/Pattern modes, each Part's receive channel is set independently as a Part parameter. The Transmit Channel parameter is selected by touching a Track button 1-16, you will transmit on the Midi channel of that particular Track output. So your mention of "OMNI" is curios. The MIDI settings in UTILITY are for Voice-Performance mode (however, the Transmit Channel parameter will reflect your most recent Song/Pattern mode selection).

We don't know MAINSTAGE (and it is their support you need) but a "MS Patch" that is setting up an ES Split/Layer... Can you give us details of an example of just one of these? Are the split and layer Parts on separate MIDI channels?

_ If yes, you have an easy option of controlling MIDI Channel Volumes... If the Parts are on different channels you can control them independently. As I'm sure you know, with channel Control Change (cc) messages: 007 and/or 011.
_ If they are on the same MIDI Channel then you must use specific channel messages to adjust the volumes independently. For example, use a specific controller to control the Voice Volume in Split Part #1 (for example, cc016), and another to control the Voice Volume in the other (cc017). Then you would need to program the individual Voices to respond to these controller numbers - within the original Voice. Or you must address the Part Volume via Sysex.
_ Does MS let you send such System Exclusive messages?
_ What Control Change messages are available to send from MS?
_ Do you need to recall specific volumes (preset) or do you additionally need to control the volumes in real time?

How are you concluding that the "volume controls on the Motif seems global", they are not. Perhaps the volume message you are sending from MAINSTAGE is globally affecting the Motif ES, or affects all Parts together because the message is a Channel-wide message. But the Parts on the Motif ES are independent, and their volumes are independently controllable.

_ Easily with dedicated Control Change channel messages (cc) -for when they are mapped to separate channels.
_ With individual assignments and messages - when multiple Parts are placed on the same channel.

Please provide just one example of a SPLIT/LAYER setup addressing multiple Parts of the ES.

thanks so much for taking the time to answer.

let me:
1) digest your response fully and then recreate issue.

i want to make sure that i am not as confused as i am. sometimes with reaponses like yours, it leads to identifying the mistake in thinking.

2) ask the mainstage forum as well.

3) lastly, re-attempt the question if any still exist.

THANKS A WHOLE LOT.

More in a few days...

It turns out, it is indeed a Mainstage(MS) question as you said, Bad Mister.

I had to make MS's "faders" "talk" to independent separate MIDI channels (corresponding to each track on my layers/splits) and assign Volume CC. These MS "faders" on the computer screen are tied up to phsyical sliders - in my case the sliders on my Korg nanoKontrol2 but the problem was the nanoKontrol2 defaults to only Channel 1 out of the box.

Solution:
I tried it on the Yamaha ES6 physical sliders (all 4 of them) and it worked. Mainstage even auto detected that each slider is controlling the Volume for each Channel - 1-4. Not much fiddling around on my part.

I now just need to make the nanoKontrol2 sliders behave like the ES6's sliders. I found some software from Korg themselves to rewrite the "scene" on the device itself, but have yet to try it.

THANKS a lot again, Bad Mister. If not for your info, questions and clarifications, it would not lead to a sensical/logical MS question in another forum and eventually to an answer.

Glad it helped!