Death metal is a subgenre of heavy metal. It began as a offshoot of thrash metal in the 1980s.-------------------Death metal is known for abrupt tempo, key, and time signature changes, as well as extremely fast and complex guitar and drumwork. Death metal may include chromatic chord progressions and a varied song structure without a standard verse-chorus arrangement. These compositions tend to emphasize an ongoing development of themes and motifs. Bands of this genre frequently utilize downtuned and distorted guitars, a downtuned, sometimes distorted bass guitar, and a drum kit almost universally using two bass drums or a double bass drum pedal. Although this is the standard setup, bands have been known to incorporate other instruments such as keyboards and saxophone. Death metal's lyrical themes typically invoke violence, but also contain various themes of Satanism, Nihilism, mythology, and even mysticism. While known for being gruesome, the lyrical subjects of songs vary greatly between bands and individual albums; bands such as Gorguts, incidentally, started out as focusing on the terror of the extremes of life in their album Considered Dead, but eventually morphed to focusing primarily on mysticism with their 1996 release Obscura. When death metal began to form in the mid-1980s, new proto-death metal bands (who played an extreme form of thrash metal) began to focus almost exclusively on the darker themes. While it may seem obvious as to how the death metal genre got its name, the source of associating this type of music with death is uncertain. There are three common theories on how death metal's name originated. The first being is the title of the Possessed’s 1984 demo called Death Metal, or the song with the same name which was featured on their 1985 debut album Seven Churches. In 1985, another song called "Death Metal" appeared on the debut album Power from Hell by thrash metal band Onslaught. A 1985 demo by Death was called Death by Metal. The second theory is that the name of genre pioneers Death was the origin of the genre's name, since their 1987 debut album Scream Bloody Gore made death metal a more recognised form. Their austere name has said to have been adopted as the genre's title. The 1984 compilation release Death Metal is also another possible origin.