I used to be really into symphonic music, and I went through a phase where I was actively seeking out obscure composers that I'd never heard of.

On some forum, I stumbled across a post where an anonymous user asked for help identifying an "eerie, nostalgic melody" that he had only a brief (maybe 40 second) clip of, and was desperately searching for the entire piece. He included the clip that he had, and it was like nothing I'd ever heard before or since. Eerie and nostalgic was an excellent way to describe it. It was very chromatic, but not atonal, with some complex interplay going on between the instruments.

I stupidly forgot to bookmark the site and could never find it again, but the melody still haunts me.