The harmonium, or pump organ, is a type of reed organ that generates sound with foot-pumped bellows. This particular organ only has one stop. Pictures of the actual instrument can be found here.
It has 3 optional repetitions (round robin) and 1 velocity layer. The volume of the actual instrument depends on the amount of air that the user puts inside using their feet. The faster the feet move, the more the volume changes. That's been modelled inside Kontakt and the user can replicate that sound using the modwheel.
Attack, release volume, sample offset, EQ, flip stereo, spread (from stereo to mono) and octave voicing controllable directly from the GUI.