Here's my scenario: I have various MIDI instruments playing on different MIDI ports (in my case, different IAC Driver ports, on OSX). All the instruments are sending on channel 1, to their respective ports. And I want to route this to a single instance of Kontakt with various virtual instruments in it, each one listening on a different MIDI channel.

I don't know if this can be done with a standalone instance of Kontakt. I'm using this from within Cubase, so my solution is to use Cubase to change the channel of each MIDI port before feeding the MIDI to Kontakt. This is done quite simply:

• Create a MIDI track. Make it listen to one of the ports.
• Add a Transformer MIDI Insert in that track.
• The first panel in the Transformer is the Filters. Here we'll add the following filter: 
  • Filter target: Channel
  • Condition: Equal
  • Parameter 1: 1 (or whichever channel that instrument is playing in)
• The second panel in the Transformer is the Actions. Here we add the following action:
  • Action target: Channel
  • Operation: Set to fixed value
  • Paramter 1: 2 (or whichever channel Kontakt expects for that instrument)
• Repeat this for each MIDI port.

(This post is for self-reference, but I publish it in case it helps somebody).