This is the main theme from the first game, X: Beyond the Frontier.
The music is not an insignificant part of why I like these games so much. As of this post, I've completed the (one and only, so far) storyline plot missions in X3 Albion Prelude and have returned to Terran Conflict in order to wrap up some of the plots I'd left incomplete when I moved on to AP. Yeah, I've been playing a whole lot of the X series lately.
