Hovland musicap capacitor: What does it do?

This sounds like a silly question and my inexperience shines right through, but I'm curious as to what they do exactly? I've recently received my Merlin speakers and they come with two pairs of musicaps. Because I'm running single wire, I only need one pair and has a spare pair sitting around. I've tried them on my sub-woofer but couldn't notice any differences one way or another. I might try the spare pair on some other places but I would like to know what they are designed for. My thanks in advance.