Strumming guitar chords with Sensors and Poly~

Hi,

I'm trying to simulate strumming chords on a midi controller I made that has various sensors.
With one sensor I am selecting the root of the chord, and with the second, an FSR, the harder I press the more chord tones get played in order of notes from lowest to highest in pitch.

I am using an SDIF file of a guitar string being plucked in a 6 voice poly~ object to get a guitar sound. My issue is that if I don't press all the way down on the FSR when I play a chord (like I only strummed 3 strings) and change root notes several notes from the previous chord will still be in the poly~. Is there a way to flush all the notes out of it after each press of the FSR? I feel like this must be a basic poly~ issue that I just don't know how to solve, but must be something pretty simple. If anyone has insight into this please let me know thank you.

Nick

My poly~ object