Question: Sanrabb is one of the founding members of which extreme subgenre of heavy metal music?

full_context: Document 1: Satan rir media: Satan rir media ("Satan Rides the Media") is a 1998 Norwegian documentary by Torstein Grude. The film covers the controversy that surrounded black metal musician Varg Vikernes in the early 1990s, who not only has been tied to a series of church arsons in Norway, but received widespread media attention for the murder of Mayhem band member Øystein "Euronymous" Aarseth.
Document 2: King ov Hell: Tom Cato Visnes (born November 27, 1974), better known as King ov Hell or simply King, is a Norwegian musician. He is best known as the former bassist of black metal band Gorgoroth, but he is also the co-founder of Ov Hell, God Seed, Jotunspor, Audrey Horne, Sahg, I and Temple of the Black Moon.
Document 3: Gorgoroth: Gorgoroth is a Norwegian black metal band based in Bergen. It was formed in 1992 by guitarist Infernus, who is also the only original member remaining, and the band have since released nine studio albums. Gorgoroth are a Satanic band and have drawn controversy due to some of their concerts, which have featured impaled sheep heads and mock crucifixions. The band is named after the dead plateau of darkness in the land of Mordor from J. R. R. Tolkien's fantasy novel "The Lord of the Rings".
Document 4: Thrash metal: Thrash metal is an extreme subgenre of heavy metal music characterized by its fast tempo and overall aggression. The songs usually use fast percussive beats and low-register guitar riffs, overlaid with shredding-style lead work. The lyrics often deal with social issues and reproach for The Establishment, using direct and denunciatory language, an approach borrowed from hardcore punk.
Document 5: Necrobutcher: Jørn Stubberud (born April 13, 1968) is a Norwegian musician. He is best known as the bassist in the black metal band Mayhem under the stage name Necrobutcher. He is one of Mayhem's founding members, along with Euronymous, Manheim and . He is the band's only remaining original member, as Messiah and Manheim left Mayhem, respectively, in 1986 and 1988, and Euronymous was murdered in 1993.
Document 6: Black metal: Black metal is an extreme subgenre of heavy metal music. Common traits include fast tempos, a shrieking vocal style, heavily distorted guitars played with tremolo picking, raw (lo-fi) recording, unconventional song structures, and an emphasis on atmosphere. Artists often appear in corpse paint and adopt pseudonyms.
Document 7: Extreme metal: Extreme metal is a loosely defined umbrella term for a number of related heavy metal music subgenres that have developed since the early 1980s. It has been defined as a "cluster of metal subgenres characterized by sonic, verbal and visual transgression". The term usually refers to a more abrasive, harsher, underground, non-commercialized style or sound associated with the speed metal, thrash metal, death metal, black metal and doom metal genres. With the exception of doom metal, all of these genres are characterized by fast tempos, attesting to their roots in hardcore punk, which has also fused with extreme metal in the forms of crossover thrash, crust punk, grindcore, sludge metal and metalcore. Though many extreme sub-styles are not very well known to mainstream music fans, extreme metal has influenced an array of musical performers inside and outside heavy metal.
Document 8: Infernus: Roger Tiegs (born on 18 June 1972), better known by his stage name, Infernus, is a Norwegian black metal musician and Satanist. He is the sole founding member and chief ideologist of the Norwegian black metal band Gorgoroth, which was formed in 1992, as well as the founder and head of Forces of Satan Records. He is mainly a guitarist, but has also participated as bassist, drummer and vocalist on several recordings released both by Gorgoroth and other bands.
Document 9: Death metal: Death metal is an extreme subgenre of heavy metal music. It typically employs heavily distorted and low-tuned guitars, played with techniques such as palm muting and tremolo picking, deep growling vocals, aggressive, powerful drumming featuring double kick or blast beat techniques, minor keys or atonality, abrupt tempo, key, and time signature changes and chromatic chord progressions. The lyrical themes of death metal may invoke slasher film-stylized violence, religion (sometimes Satanism), occultism, Lovecraftian horror, nature, mysticism, mythology, philosophy, science fiction, and politics, and they may describe extreme acts, including mutilation, dissection, torture, rape, cannibalism, and necrophilia.
Document 10: True Norwegian Black Metal – Live in Grieghallen: True Norwegian Black Metal – Live in Grieghallen is Gorgoroth's first full-length live album, released by Regain Records. It was recorded live in the studio at Grieghallen Lydstudio in Bergen and Threeman Recordings in Stockholm. The songs on the album represented the most commonly played songs in Gorgoroth's live set. The cover design by Magnus Wohlfart was radically different from the previous three full-length albums, being more reminiscent of the cover of the album "Under the Sign of Hell" (1997). Most of the album was recorded before the departure of vocalist Gaahl and bass guitarist King ov Hell, who had intended on using the band's name and assets. The bass guitar for this album (originally performed by King ov Hell) was later re-recorded by guitarist and band founder Infernus. Infernus dedicated the album to the late Jon Nödtveidt of Dissection.
Document 11: Euronymous: Øystein Aarseth (] ; 22 March 1968 – 10 August 1993), who went by the pseudonym Euronymous, was a Norwegian guitarist. Euronymous was a founder of and central figure in the early Norwegian black metal scene. He was a co-founder of the Norwegian black metal band Mayhem. He was also founder and owner of the extreme metal record label Deathlike Silence Productions and record shop Helvete.
Document 12: Black Metal (Venom album): Black Metal is the second album by English heavy metal band Venom. It was released in November 1982, during the great flourishing of metal music in the UK that was the new wave of British heavy metal, and is considered a major influence on the thrash metal, death metal and black metal scenes that emerged in the 1980s and early 1990s.
Document 13: Sanrabb: Sanrabb is a Norwegian black metal musician and one of the founding members of black/death metal band Gehenna.
Document 14: Nu metal: Nu metal (also known as nü-metal and aggro-metal ) is a form of alternative metal that combines elements of heavy metal music with elements of other music genres such as hip hop, alternative rock, funk and grunge. Nu metal bands have drawn elements and influences from a variety of musical styles, including multiple genres of heavy metal. Nu metal rarely features guitar solos; the genre is heavily syncopated and based on guitar riffs. Many nu metal guitarists use seven-string guitars that are down-tuned to play a heavier sound. DJs are occasionally featured in nu metal to provide instrumentation such as sampling, turntable scratching and electronic backgrounds. Vocal styles in nu metal include singing, rapping, screaming and growling. Nu metal is one of the key genres of the new wave of American heavy metal.
Document 15: Grindcore: Grindcore is an extreme genre of music that originated in the early to mid-1980s. It draws inspiration from some of the most abrasive-sounding genres, including hardcore punk, extreme metal, industrial and noise rock. Grindcore is characterized by a noise-filled sound that uses heavily distorted, down-tuned guitars, grinding overdriven bass, high speed tempo, blast beats, and vocals which consist of growls and high-pitched shrieks. Early groups like Napalm Death are credited with laying the groundwork for the style. It is most prevalent today in North America and Europe, with popular contributors such as Brutal Truth and Nasum. Lyrical themes range from a primary focus on social and political concerns, to gory subject matter and black humor.
ground_truth: Black metal