Cheers for that
Yea, basically it's an old AKAI SG01v which is daisy chained from the THRU port on the Korg EA-1.
The Korg receives channels 1 and 2 only, the AKAI accepts channels 1-16 without an option on the panel to turn off the reception.
The message I need to send is $F0 $47 $10 $42 $5D(AKAI) $40 $1r $02 $vv
r = part number (1-16)
vv = reception channel (1-16 with anything over 16 being 'disable')
I've figured out you can simply enter that, over writing the "Ch" "Num" and "Val" fields, but it's not easy, if there's a value already in there, you have to drag it to $00 before you can double click and enter data.
And yes, I've run out of MIDI ports