Acid rap is a subgenre of alternative hip hop in which lyrics are often cryptic, abstract or abnormal, trippy or psychedelic, spacey, dark or sinister, and sometimes drug or science fiction-related, with eerie or spaced-out drumbeats and instrumentation. It can sometimes include direct or indirect references to science fiction, outer space, and futuristic themes, such as Afrofuturism, space or time travel, and extraterrestrials. However, acid rap usually encompasses a wide variety of strange or abstract themes.
This form of "acid rap" is not directly related to the Bristol-based genre of trip hop, but shares many similarities, especially in instrumentation. In fact, the two genres often overlap.
Rapper El-P's discography, such as the recent I'll Sleep When You're Dead, is a prime example of acid rap, as is much of collaborator Cage Kennylz's work. Aesop Rock, another Definitive Jux artist, also has intensely abstract lyrics that can be considered acid. The British artist Tricky is often considered trip hop, but fits easily within the acid rap genre as well due to his unique trippy rapping style. Edan's Beauty and the Beat also has some acid rap elements. Many rap artist who sample space rock or psychedelic music can also be considered acid rap.
Esham, an underground Detroit rapper, specializes in a genre of rap he has dubbed "acid rap." Esham has defined the genre as analogous to "'modern day blues [or] heavy metal'". Esham's self-proclaimed acid rap shares many similarities with the genre commonly known as acid rap, such as eerie and dark subject matter and trippy beats. Esham has even collaborated with frequent acid rapper Kool Keith on his 2001 release, Tongues. Esham is known for his hallucinogenic style fusing rock-based beats and lyrics involving trippy subjects. Esham's genre of "acid rap" also fits comfortably in the hardcore hip hop and horrorcore categories, as it often involves eerie mind-bending lyrics about sex, drugs, paranoia, murder, gore, and the occult. Followers of Esham include Eminem, who was associated with and often placed in the acid rap genre early in his career prior to his widespread popularity.
Alternative names for acid rap include "space rap," "stoner rap," and "trip hop," though trip hop usually refers to the ambient Bristol music genre.