Q: Why do my Volume Sliders not control Volume for a Part or Element?
A: Because that Part or Element's Volume Parameter is ASSIGNED to a different Controller in the Control Assign matrix.
For the Slider to work again, you will need to DELETE the Assign*.
Use the Reference Manual to guide you through searching for and deleting Control Assigns.
*This is true even if the Assign Control is "non-functional", e.g. Ratio=0, or assigned to non-existent controller (e.g. Breath Controller).
Very often, Factory Preset Performances were "Built" from pre-existing Parts or Performances. This means those pre-existing Control Assigns are also still embedded in the "New" Performance.
For whatever reason, the Yamaha sound designers chose not to DELETE these redundant Control Assigns. Rather they chose to negate their functionality (e.g. Ratio = 0), or just leave them as is.
You will nearly always find redundant control "debris" in Factory Preset Performances.
Good Practice on the MODX, before committing to a Sound Design project, is to "House Clean" the Control Assign matrix. Delete everything you don't need, or as I do, just delete everything.
Learning and Understanding the MODX "Mod Matrix" is vital to smooth and enjoyable operation. ????
Having the wrong mode of Slider Operation engaged (Element/Operator instead of Part) and/or having MIDI set to DAW are (I'd suggest) more likely causes of this behaviour.
@Andrew... that is another reason. Most likely? Subjective.
I can say that a MODX User will likely encounter the "Control Assign" issue within the first 60 minutes of ownership, not least because the provided Owners Manual steps you through creating a Cross Fade with Control Assigned Part Volumes. Shortly after which, you realise the Volume Slider doesn't work.
But the same "instant puzzlement" could be said of any Brand New User eagerly browsing through the Presets, since nearly all Presets have Volume for one or more Parts "assigned".
Unsurprisingly, their first reaction is likely to be "the Slider is broken".
I really do think Yamaha need to make this clear early on in their customer's experience.
I would recommend an Attention Call Out Box is placed in the Owners Manual (I.e. the First Manual you are likely to read).
Manuals won't/don't/can't help with this, significantly.
A drop down popover such as shows up when editing the value of a cutoff or other value that shows at the top as a pop down, that's what's needed... with info.
eg. you slide the slider... a little warning rolls down:
"Slider Action overridden by Part AssignKnob 3"
If you click on this rolldown, whilst it's showing, it should take you immediately to the mod section at AssignKnob 3 of the Part, so you can edit or delete this assignment.
Consideration, Conventional Consistency and Convenience!
"Slowdown..." I hear you say. "that's not the Yamaha Way™"
But wait, there's more:
Similarly, if MIDI is over-riding usage of the Sliders, a rolldown popover shows a warning informing of this, and is "clickable" and takes the user to the MIDI setup.