Ok, so I’ve wired up the choir manual to the MIDI scanner, plugged the scanner into the MIDI controller, given that some volts, plugged it into the MIDI-to-USB converter, and I am now watching MIDI messages appear on my laptop screen.  They’re all in the wrong order, which is vexing and requires further consideration.  At the moment it’s a bit like this (from imgur, alas I don’t know the creator):

But the important thing is that I NOW HAVE MIDI MESSAGES GOING FROM THE KEYBOARD TO THE COMPUTER!

This pleases me greatly, and I am going to have a cup of tea.  With a celebratory biscuit.