It's always nice to have some thematic background music on while playing a game, but I've gotta say no pairing pleases me quite as much as Brass + Brass Band music.
The music itself is both non-distracting and suitably epic. The fact that the genre has the word "BRASS" in it is icing on the cake. Furthermore, the music is also historically and thematically appropriate: British brass bands became popular during the era that the game covers, in the region the area covers, and their members often were the coal miners and factory workers that work so hard to flip our ports for us.
I just really love how perfectly these two fit together.