Oddly enough, I find movie soundtracks to be the single most distracting music selections during work. I constantly find myself zoning out and thinking about movie scenes. For me, a soundtrack carries a heavy emotional weight similar to watching the movie itself. In the case of LoTR, I get this crazy nostalgic feeling and have a strong desire to watch LoTR again. Great movies.

I find that albums I have listened to more than 15 or 20 times help me focus the most during work or study. New albums and hip-hop both tend to distract me.

Edit: clarity