Everything we posted above is a way to do the "job" in various ways.. I finally had a few minutes to think more about the situation and came up with this approach. Without trying to confuse, I would suggest looking at the following as perhaps a better way (system) considering all of the situation:esp being this is the first conversion.
These system boards come from Midi-Hardware
https://www.midi-hardware.comand are designed to be easy to install, esp using the .WIPLUG adapters. Together they will Midi-fy 2 -manuals, 1 pedal board and up to 3 expression pedals.
Would suggest you look over all of these suggestions, esp the user manuals. Everything listed is basic and straight forward. Total cost is listed in USD.
Future additions could be for controls such as stop control, thumb and/or toe pistons, touch screens, Launchpads etc,etc,etc. For now you may want to nual wiring using the majust concentrate on the basics.
There is, of course the computer, and audio system for later as well. Granted, there is quite a lot to "digest" but it is doable. Just don't get overwhelmed. As the saying goes "Rome wasn't built in a day" and neither is a good Hauptwerk system.
2 - BBS-1K - Bus Bar Scanner - price: 54.00 USD (66.42 incl.VAT) each, X 2 needed - 1 for each manual
https://www.midi-hardware.com/index.php?section=prod_info&product=BBS-1K&R2=USD4 - WIPLUG adapter -, price: 9.60 USD (11.81 incl.VAT) each X 4 needed - 2 for each manual
https://www.midi-hardware.com/index.php?section=prod_info&product=WIPLUG&R2=USD1 - MRG2 - Master Controller - price: 57.60 USD (70.85 incl.VAT) 1 needed for the system
https://www.midi-hardware.com/index.php?section=prod_info&product=MRG2&R2=USD1 - BBSP - pedal board control - price: 36.00 USD (44.28 incl.VAT) 1 needed for the pedal board
as well as up to 3 expression pedals
https://www.midi-hardware.com/index.php?section=prod_info&product=BBSP&R2=USDRgds,
Ed