Trap music, also known simply as trap, is a subgenre of hip-hop music that originated in the Southern United States. Lyrical references to trap began appearing in 1991, while the modern sound of trap emerged in 1999. The genre takes its name from the Atlanta term "trap house", a drug house. Trap music features simple, rhythmic, and minimalistic production that uses synthesized drums. It is characterized by drum beats with complex hi-hats, snare drums, and bass drums, some of which are tuned with a long decay to emit a bass frequency, originally from the Roland TR-808 drum machine.