Death metal is usually identified by extreme brutality and speed. The vocals, or growls, as they're often called, are rough and/or incomprehensible and they usually communicate macabre subject matter. This style of music is known for very abrupt tempo and count changes, and extremely fast drumwork. Most bands of this use guitars and drums, often two rhythm guitars, a bass guitar, a drum set, and a vocalist. Some bands add incidental synthesizers for effect. Lyrics tend towards extreme, unpopular worldviews and profound violence. The intense focus on morbidity likely inspired the naming of this genre as "Death" metal.