Sound familiar?

If not exactly, it sure seems to me that some of the background Mark Snow-esque music was at least inspired by Tchaikovsky's Andante cantabile, especially for Scully's part of the storyline.

I can't say that I've ever stuck around long enough to see if it's acknowledged in the music credits, but maybe it's already there. I'd just heard it recently, and it got me to asking myself where I'd heard it before because it sounded so familiar to me.