Hello, Piano64!

I'm using a K2000! So, I don't really know if I can help you. In my K2000 I have several controller settings like Breath (breath control) or Foot (foot switch). If you want to use a foot switch for the sound on this midi channel than you'll have to set this controller for the filter you want to control. On your K2600 it should be the same procedure like setting a Mwheel (modulation wheel) or Pitch (pitch bend).
Good luck!

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Greetings from Frankfurt (Germany),
Sheriff ;-)