pfilter is a variable state filter, triggered between 2 adjustable cut-off values by a tempo-sync'd probability-based step sequencer.

Choose from 8 to 16 steps per bar (measure) and the probability of triggering the cut-off (from 0% to 100%) for each step. As the track plays, the filter will loop through the steps and randomly trigger the cut-off depending on the probability assigned to each step.

You choose a lower and an upper cut-off value, the lower value is the default (unless the invert button is pressed) and the upper value is triggered according to the step sequencer

http://www.delamancha.co.uk/pfilter.htm
http://www.delamancha.co.uk/plugins/pfilter.zip