Okay, so here's the relevant notation:
It's generally described as playing them held but with a pulsing feel that still suggests some separation.
I have (had) formal training on saxophone and upright bass. I know how I would approach this on either of these (via control of breath or bow). But I'm at a loss as to how to play it on piano ...
Is this even a thing that can be done on piano? If not, why does the piece I'm currently working on have this notated?!
Enthusiastic but mediocre amateur.