One song you're bound to hear more than once in this movie is "I'm Shipping Up to Boston" by the Dropkick Murphys. Like this movie, the song is super Irish and super aggressive. Just about all the music in this movie has an Irish flavor—even the Spanish-influenced melody of "The Departed Tango," composed by Howard Shore. If you ever have some friends over for Saint Patrick's Day, you can actually just go ahead and throw on this movie's soundtrack from start to finish.