Stoner doom, stoner metal or psychedelic doom describes doom metal that incorporates psychedelic elements, to varying degrees. Stoner doom is often bass-heavy and makes much use of guitar 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.
Drone doom (also known as drone metal) is a style of doom metal that is largely defined by drones; notes or chords that are sustained and repeated throughout a piece of music. Typically, the electric guitar is performed with large amounts of reverb and feedback while vocals, if present, are usually growled or screamed. Songs are often very long and lack beat or rhythm in the traditional sense. Drone doom is generally influenced by drone music,noise music and minimalist music. The style emerged in the early 1990s and was pioneered by Earth,Boris and Sunn O))).