 Unaware of the fact that the sound she had asked for in "I Knew You Were Trouble" was actually dubstep, Swift recalled having listened to dubstep music presented to her by British musician Ed Sheeran, who played her the songs popular in the UK clubs.However, she confessed that she had not studied that particular genre of sound further.According to Sarah Maloy from "Billboard", "I Knew You Were Trouble" is a departure from Swift's characteristic country songs, and blends pop and dubstep in its composition, The song begins as a typical pop rock, sock hop music with jaunty guitar sounds and Swift singing the lyrics which describes the early stages of a romantic affair; the tune soon changes its composition.