Stoner doom, stoner metal and psychedelic doom describes doom metal that incorporates psychedelic elements, to varying degrees. Stoner doom is often bass-heavy and makes much use of guitar/bass effects such as fuzz, phaser or flanger. Stoner doom could be viewed as the heavier and slower form of stoner rock, as the two styles emerged simultaneously. It was pioneered in the early–mid 1990s by bands such as Kyuss, Sleep, Acid King, Electric Wizard and Sons of Otis.