Let me throw out something else. If you have one of the SPX reverbs as an insertion effect - then you could send MIDI commands to either route individual elements through this insertion effect or to bypass it. This would be an ON/OFF deal (completely "wet" or completely "dry" with respect to reverb ) but individual for each element.
You would use this:
0x41 / ep / 0x17 -- Element Connection Switch with value 00=Thru (bypass BOTH InsA and InsB), 01=Connect to InsA, 02=Connect to InsB
Where:
a) 0x41 = the high address ("ah" ),
b) ep, as the middle address ("am" ) is decoded as upper-nibble ("e" ) is element number 0-7 to cover elements 1-8 and lower nibble ("p" ) is 0x0-0xF (0-15 decimal) which represents the part number.
Hex makes upper nibble and lower nibble easy to construct. A hex value of 0xUL - the "U" is a hex digit 0-F and is the upper nibble. In other words, the first "digit" in a hex value with two digits is always the upper nibble. And the "L" as a hex digit 0-F is the lower nibble.
"ep" as 0x17 means element number 2 (value 0=element 1, value 1=element 2, and so on) and PART number 8 (0=part 1, 1=part 2, and so on).
c) 0x17 = the low address ("al" )
Rest of the sysex command is standard fare - although can walk through that if needed. Reference
https://www.yamahasynth.com/ask-a-question/how-to-send-sysex-commands-to-montage for some detail.
Say you had insertion routing like this:
InsA --> InsB --> Mixer (next step in audio chain - rest through to final out)
Then "Thru" would be
Element X "Dry" Out --> Mixer (note: skips both InsA and InsB)
"InsA" would be:
Element X "Dry" Out --> InsA --> InsB --> Mixer
"InsB" would be:
Element X "Dry" Out -> InsB --> Mixer (skips/bypasses InsA)
So if you placed an SPX Reverb on InsA - then you could bypass it by setting this parameter to "InsB" (or value=02).
The default value is 01 (InsA).