is it as you are playing a note sequence on the piano roll? or on a keypad, i learned it was from a sound stopping not at a specific point before it stops, i think at 0 decibles?? and that creates a pop and you need to adjust the cutoff. the amount, release and stuff you need to adjust in the envelop editor to full on amount i think and at least 0.1 on release, i think attack is for pops at the beginning, you can play with these values