Technical death metal (also referred to as tech-death) is a musical subgenre of death metal with particular focus on challenging, demanding instrumental skill and complex songwriting. Experimentation in death metal began in the late 1980s and early 1990s by four bands that are often grouped together as "technical death metal's Big Four" – Death, Pestilence, Atheist, and Cynic – as well as Nocturnus; all but Pestilence being part of the Florida death metal scene.^[2][3]

Some of the distinct features of this genre include dynamic song structures, complex and atypical rhythmic structures, abundant use of diminished chords and arpeggios, frequent employment of odd time chord progressions, and consistent use of string skipping on the guitars. Bass lines are usually complex, and drumming is complex including techniques such as blast beats, odd time signatures and double kicks. The technical death metal genre has also been influenced by mostly jazz fusion,^[1] as well as thrash metal and progressive/technical-inspired heavy metal bands like Death,^[4][5] Megadeth,^[6] Slayer,^[4][7] Voivod,^[8] Kreator,^[5] Dark Angel,^[6] Coroner,^[5] Sadus,^[9] and Watchtower, the latter of whose second album Control and Resistance (1989) is often considered to be one of the sources of inspiration for the genre.^[10][11]

The 1990 album The Key by Nocturnus has been cited as the first progressive death metal album.^[12] One of the key works that cemented the subgenre was Atheist's debut album Piece of Time, also released in 1990, which took death metal into a more intricate level while incorporating influences ranging from jazz fusion to progressive metal. In 1991, New York death metal group Suffocation released their debut album Effigy of the Forgotten, which focused on pairing speed and brutality with a "sophisticated" sense of songwriting. Atheist's second album Unquestionable Presence, Pestilence's third album Testimony of the Ancients, and Death's fourth album Human were all released the same year, forging a path for more intricate and refined releases within the death metal genre.^[3]