As it happens, just today I got a reply from Roland support with a couple of methods. Gonna try them this evening, and if one or both of them work, I’ll post the information here for others to use.
[/quote]
Here’s the answer from Roland:
“Thanks for reaching out and contacting Roland BOSS USA Operational Product Support about the ES-8 and MD-500.
So first off, for the MD-500 ROTARY control, it's designed like the old Leslie speaker in the sense there's only a SLOW and FAST SPEED with associated rise and fall parameter.
So you can program and use an ASSIGNMENT in the MD-500 for the TAP CTL, CTL1 or CTL2 to control the ROTARY SLOW/FAST speed change.
You can then use either a cable connection from the ES-8 CTL 1/2 output jack via 1/4" TS stereo cable to control the CTL 1/2 jack foot switching on the MD-500 or you can use a MIDI CC# from the ES-8 via 5 pin MIDI CABLE output to MD-500 MIDI INPUT, to control the MD-500 CTL1 CC: CC#80 set to control rotary speed via ASSIGNMENT.
This is a two part setup part MD-500 and other part on the ES-8.
MD-500 SETTINGS ASSIGNMENT FOR CTL1:
On the MD-500 choose a PATCH you have the ROTARY MODE set up and you want to control the ROTARY SPEED.
Press EDIT, use up/down arrows to locate CONTROL and press EDIT, make sure the CTL1 and 2 PREF/PREFERENCE: is set to PATCH and not SYSTEM/GLOBAL.
This way the CTL1 ASSIGNMENT will only work on this specific PATCH. Set the CTL 1 and 2 FUNCTION: OFF, press EXIT, arrow down to ASSIGN and press EDIT.
Set ASSGN1 SW: ON, this will open the ASSIGNMENT 1 parameter options menu.
Set ASSGN1 SW: ON
SRC: CTL1 PDL
MODE: TOGGLE
TRG/TARGET: ROTARY SPEED
MIN: SLOW
MAX: FAST
WRITE/SAVE these settings to this specific PATCH by pressing the WRITE button [EXIT+EDIT} and EDIT once more to WRITE/SAVE the customized user settings.
You can now connect the ES-8 CTL 1/2 OUTPUT to the MD-500 CTL 1/2 INPUT via 1/4" TRS STEREO CABLE.
For example:
https://www.boss.info/global/products/bcc-3-tra/
ES-8 PATCH SETTINGS FOR MUTE FUNCTION TO CONTROL CTL 1 OUTPUT:
On the ES-8, you can commandeer and use the MUTE footswitch for example to control the CTL1 jack ON/OFF of the ES-8.
Choose an ES-8 patch you want to correlate with the MD-500 ROTARY MODE patch,
Press EDIT, navigate to the CTL/EXP menu and press ENTER, navigate left/right to MUTE and press ENTER.
Change the default MUTE functionality from MUTE to CTL1:
Set: MIN: OFF, MAX: ON, MOD/MODE: TGL/TOGGLE.
WRITE/SAVE these settings to this specific PATCH by pressing the WRITE button three times to WRITE/SAVE the customized user settings.
Now should be able to use the MUTE footswitch to control the ROTARY SPEED for the PATCH, the MD-500 display will show the change from SLOW/FAST.
ES-8 MIDI CONTROL FOR MUTE ASSIGNMENT TO SEND MIDI CC# FOR MD-500 CTL1 FUNCTION FOR ROTARY SPEED:
Alternately, if you'd like to control the same MD-500 CTL1 PEDAL FUNCTION AND ASSIGNMENT you can use the default MIDI CTL1 CC: #80 to control the CTL1 ASSIGNMENT functionality.
(See MD-500, EDIT > MIDI > CTL1 CC: CC#80 default).
Use the ES-8 to send a MIDI CC# with the MUTE footswitch.
First turn the default MUTE control functionality to OFF.
Press EDIT, navigate to the CTL/EXP menu and press ENTER, navigate left/right to MUTE and press ENTER.
Change the default MUTE functionality to OFF.
Press EXIT and navigate in the CTL/EXP menu to ASSIGNMENT 1 and press ENTER, program the ASSIGN1 in the following manner:
ASSIGNMENT1 SW: ON
SOURCE: MUTE
MODE: MOMENTARY
CATE/CATEGORY: MIDI
CH: MIDI CHANNEL 1 ( or MD-500 MIDI CH)
CC: CC#80 to target the CC for the MD-500 CTL1 ON/OFF for control of the ROTARY SLOW/FAST.
WRITE/SAVE these settings to this specific PATCH by pressing the WRITE button three times to WRITE/SAVE the customized user settings.
Connect the ES-8 MIDI OUTPUT to MD-500 MIDI INPUT using a 5 pin MIDI cable.
For example:
https://www.boss.info/global/products/bmidi-pb1/
Now should be able to use the MUTE footswitch to MIDI control the ROTARY SPEED for the MD-500 PATCH via MIDI CC#, the MD-500 display will show the change from SLOW/FAST.
Choose TRS cable or MIDI cable connection and programming for controlling the ROTARY SPEED of the MD-500, one or the other.”
