Sludge metal is a form of heavy metal music that is generally regarded as a fusion of the doom metal and hardcore punk genres, often displaying southern rock influence. Sludge metal is typically aggressive and abrasive; most often featuring shouted vocals, heavily distorted instruments, sharply contrasting tempos and complex drumming. It originated in the American state of Louisiana during the late 1980s.
Sludge metal generally combines the slow tempos, heavy rhythms and dark, pessimistic atmosphere of doom metal with the aggressive style, shouted vocals and fast tempos of hardcore punk. The string instruments (electric guitar and bass guitar) are heavily distorted and often use a large amount of audio feedback to produce an abrasive, sludgy sound. Guitar solos are often absent. Drumming bears similarities to the style of drumming present in hardcore punk or extreme metal; for example d-beat and double bass drumming. However the beats may be slowed considerably, with the tempo usually falling somewhere between 50 and 80 beats per minute (bpm). Vocals are usually shouted or screamed, and lyrics are generally blue-collar in nature; reflecting on society, generally in a depressive, cynical or downtrodden manner.
Many sludge metal bands from the Southern United States incorporate southern rock influences and imagery, although it should be noted that not all sludge metal bands share this style. Due to the similarities with stoner metal, there is often a crossover between the two genres, but sludge metal generally avoids stoner metal's positive atmosphere and its usage of psychedelia. Sludge metal also bears some musical and lyrical resemblance to crust punk (for example Dystopia).
Sludge metal has several loosely defined subgenres. Traditional sludge metal is the "purest" form of the genre, typified by bands such as Crowbar, which come from New Orlean's metal scene. Southern Sludgecore is typified by strong blues and southern rock influences, extreme levels of distortion, extremely slow tempos, and generally hateful and controversial lyrics concerning misogyny or drug addiction. Eyehategod is generally regarded as the founder of this genre. Aside from Louisiana, the biggest sludge metal scene is in North Carolina. North Carolina bands usually have a stronger punk influence, which includes bands such as Corrosion of Conformity, Antiseen, Weedeater and Buzzov*en. It is important to note that not all sludge metal is slow. The term Sludge/Doom is usually applied to sludge metal bands that emphasise low-tempos.
Atmospheric sludge metal aims to produce an ambient atmosphere with reduced aggression, more philosophical lyrics and an experimental style. Neurosis, Isis and Cult of Luna are considered the forerunners and the most important bands in this subgenre. Atmospheric sludge bands draws influences from bands such as Earth, Neurosis and Godflesh instead of the earliest sludge metal bands. Mogwai in particular are a strong influence, especially on Isis, Cult of Luna, Pelican and Callisto. Mogwai's influence is particularly demonstrated by the use of single-note delayed guitar riffs which are achieved using a delay pedal. In an interview, Pelican mentioned that the heaviness of their music is no longer their main priority. Their sound is now being referred to as post-metal or "postcore" by many fans.
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