My apology for trying to keep the title short.
When you release a key but hold the sustain pedal, the key will keep glowing.
I was experimenting with your rendition of Chasse-Neige when I discovered this.
I dunno if it will do the same after rendering, but the preview just looks unnatural to me...
Warning: Wall of image approaching
I deleted all particles and sabers to make it more obvious.
Turning off “Sustain Hold” in Keyboard Settings will fix this.