Technical death metal (also called tech death for short or also can be known as Progressive death metal), is a term used to describe bands in the subgenre death metal that focus on more complex rhythms and song structures. As death metal bands began further exploring the genre, they experimented with a variety of song structures, tempos, and playing techniques from other genres to create music that changed the style. As a result of such experimentation, such as the works of Cynic and Atheist, the subform of tech death established itself as a complex and varied musical style.
Technical death metal incorporates a variety of influences from genres such as jazz fusion, progressive rock and European classical music into general death metal aesthetics to compose music that is thought to be unexpected, difficult to play and often difficult to comprehend. Songs tend to be written without distinct choruses, with varied or layered time signatures, and sometimes dissonant or atonal guitar riffs.
More technical experimentations in death metal started in the late 1980s and early 1990s by bands such as Death, Morbid Angel, Monstrosity, and Atheist. In 1989 Atheist's debut album Piece of Time came out followed by Nocturnus's The Key in 1990. In 1991 Death released Human. This album and later Death albums have proven influential on 1990s technical death metal bands. Other early technical death albums are Considered Dead (1991) by Gorguts, Nespithe (1993) by Demilich and Focus (1993) by Cynic. While Cynic became recognised for their technicality, it wasn't fully understood until the mid 1990s when other bands created music that furthered what were then the borders of death metal.