Ordo Ad Chao is the fourth full-length album by the Norwegian black metal band Mayhem. The album received the Spellemann Award for best heavy metal album on 2 February 2008. It is the first Mayhem album with the vocalist Attila Csihar since the 1994 album De Mysteriis Dom Sathanas and the last with Blasphemer before he announced his departure from the band in 2008. The drummer, Jan Axel Blomberg (Hellhammer), said that the drum tracks were not equalized and only the bass drums were triggered. He ended saying "the production sounds necro as fuck, but that's the way we wanted it – this time. It represents Mayhem today." Indeed, the sound of the album is much rawer than that of any official Mayhem studio release since Deathcrush, with a very bass-heavy mix. Despite that, the album continues the somewhat unorthodox songwriting approach showcased on the band's last two releases, with "Illuminate Eliminate" being the band's second longest song. The album includes some death grunts and clean vocals; however, Grand Declaration of War has cleaner vocals.