Horrorcore is a subgenre of hip hop music based on horror-themed and often darkly transgressive lyrical content and imagery. Its origins derived from certain hardcore hip hop and gangsta rap artists, such as the Geto Boys, who began to incorporate supernatural, the occult, and psychological horror themes into their lyrics. Other early originators and influences on the genre include Gravediggaz, Flatlinerz, Three 6 Mafia, Brotha Lynch Hung, Tech N9ne, Necro, and Kool Keith.