Kid Cudi made melodic introspection an influential new sound and inspired countless imitators. His psychedelic experimentalism can be heard in the echoing distortions of Travis Scott's electric, unpredictable "90210." The then-18-year-old Khalid's delicate, homespun "Location" attests to Cudi's melodic inventiveness; this sound shimmers darkly on Kanye's frequently covered "Heartless," in which his voice breaks into jagged Auto-Tune shards.