“Sicko Mode” by Travis Scott was an unexpected chart topper. It sounds more like three songs than one. Its disjointed otherworldly effects, echos, and song structure are a far cry from the pop songs we’re used to, but it’s in these off-kilter moments that we get glimpses of a musical culture built on sonic experimentation that has had a massive impact on nearly every genre for the past 50 years: Jamaican dub.