Some of the music I habitually use, usually by player request:
Adagio for Strings - depicts the loneliness of the deep dark between the stars.
Ring of Fire (Johnny Cash) - The first time I ran a multiple-craft combat (several fighting vessels on both sides), this music happened to to be playing, loudly, on a neighbor's sound system, and the players loved it. It's become something of a tradition.
various recordings of Taiko drums, played mainly when a ship is entering atmosphere for whatever reason (landing, GG refueling, etc.)
Any time the PCs are heading into a starport town for "a nice night among the locals," the music that starts everything off is almost always Presley's "Viva Las Vegas!" Especially since the movie "3000 Miles to Graceland" came out.
There is one rather large family of free traders based on Heinlein's Merchant Families of "Citizen of the Galaxy" that are aurally represented by bluegrass music. Since they own a fairly wide variety of starships, including a truly hard-used Type-T (only two turrets operational), they frequently find themselves competing with the PC group for cargo, passengers, etc. On the other hand, some Family members have pulled the PC's chestnuts out of the fire on a couple of occassions, but there's a whole lot of backstory to those that the PCs don't know yet, and I know they read this on occassion. Even so, the players truly hate to hear "Dueling Banjos," and not just because of the movie "Deliverance."
Simon Jester