If you link keyboard-tracking to a destination and set the modulation intensity the following should happen:
mod-intensity: positive --> the parameter increases according to the keys pressed (higher key, higher positive value)
mod-intensity: negative --> the parameter decreases inverse to the keys pressed (higher key, higher negative value)
If you link the cut-off of the filter positiv to the keyboard, the cut-off will follow the keys accordingly. At lower keys the cut-off will be lower and will get higher, when higher keys are played. In other words, a LP filter opens and a HP filter closes with higher keys.
The exact starting position of the effect is defined by the cut-off setting of the filter and the mod-intensity of the data knob.