In my experimental solution above (the 3rd post), the Rescale modifier successfully inverted the values from the expression pedal (MIDI CC 11), with the following settings:
Kind: Control Change
In Low: 0
In High: 127
Out Low: 127
Out High: 0
However, the following settings did not successfully invert the MIDI output values, which remained 0 when the expression pedal is not depressed, to 127 when the expression pedal is fully depressed:
In Low: 127
In High: 0
Out Low: 0
Out High: 127
So while the “Out” parameters seem to be interchangeable, using low/high OR high/low values for its two parameters, the values for the “In” parameters seem to require a lower value as the first parameter and a higher value as the second parameter.
It might be nice for there to exist a dedicated “CC Invert” modifier for MIDIhub which would invert a set of two values (such as 0 and 127, or 24 and 68), or the numbers of a range of values (such as 0-127, or 12-48).
A “CC Inverter” modifier might include two parameters for example, the first to specify which MIDI CC number(s) to apply the inversion to, and the second to specify which of two values or a range of values to invert. For example, the second parameter could be programmed to be user-edited to contain either a comma separated list of two values (like 0, 127 or 56, 12) or a hyphen-separated range (like 0-127 or 64-84). In the first (comma-separated) example, the modifier would invert the first value to the second value and vice versa (0 to 127 and 127 to 0, or 56 to 12 and 12 to 56), and in the second (hyphen-separated) case the modifier would invert each value within the range to its opposite (only the middle value of an odd-number range would remain unchanged).