Interesting thing I noticed about this movie

There's a tune that plays at various points throughout the movie, I think it's the theme song. It's interesting because it plays over the movie here and there, but then when Roger takes Nick to the brothel, the song is being played in the club (as in the real world of the movie, not added in over it).

It's kind of like the song is building up to the low point of where Roger and Nick find themselves in the movie.