This should be something in the manual. I'll try to add it but I wanted to state it here.
A quick word about logarithmic audio controllers:
With the exception of our built-in audio logarithmic volume controllers (for which we have the luxury of
having a minimum slider decibel Global Setting), some logarithmic plugin controllers specify a minimum value of 0.0.
This presents a problem: When we want to display or manipulate (increment, adjust) the value in units of decibels,
there is no specification of what a reasonable minimum decibel value would be.
No plugin architecture has such a specification for this value.
A minimum decibel value MUST be chosen before any math can be performed in units of decibels.
It cannot be -inifinte decibels as the stated 0.0 minimum log value suggests.
Otherwise you end up with NAN infinite values and so on.
When a plugin's minimum log value states it is 0.0, it implies that it is up to the user (or the app) to choose a minimum decibel value.
Unfortunately MusE doesn't have per-controller user-settable decibel minimums and maximums.
And, well, it would be a lot of user micro-management. Without an 'overview' window, the user might be lost, unsure of
how many of the potentially hundreds of controllers available have what particular settings.
So I had no choice but to 'compose' or 'educated guess' pick a minimum decibel value based on the overall value range of the controller.
What this means is that a logarithmic native UI control might jump to -infinite dB a bit too soon when its corresponding generic UI control
is moved towards zero.
Try it with LSP plugins for example. Some of their plugin native UIs have 'level' controls which, when rotated clockwise,
jump from -infinite dB to -80 dB, and then smoothly rise to say, 60 dB.
But our generic UI version of that control has no way of knowing that the plugin's minimum dB value is -80 dB
before it jumps down to -infinite dB. There is no specification of that value in any plugin architecture (LV2, VST etc.).
Therefore the semi-educated minimum dB value that I pick in my code might be somewhat higher than -80dB.
This means the native control might jump a bit too soon from a minimum value that I pick of say, -60dB, down to -infinite dB,
as the corresponding generic UI control is lowered.
The exact same rules apply to midi-to-audio controller assignment discussed in this thread.
You may see the native UI control jump a bit too soon to -infinite dB as the the external midi controller is lowered.
Hope you can understand that.
I need to explain it a bit more in the manual.
Tricks, traps, and gotchas for sure.