Math Rock

A rhythmically complex, often guitar-based, style of experimental rock and indie rock music that emerged in the late 1990s, influenced by progressive rock bands like King Crimson and 20th century minimalist composers such as Steve Reich. It is characterized by complex, atypical rhythmic structures (including irregular stopping and starting), counterpoint, odd time signatures, angular melodies, and extended, often dissonant, chords. math rock frequently uses asymmetrical time signatures such as 7/8, 11/8, or 13/8, or features constantly changing meters based on various groupings of 2 and 3. This rhythmic complexity, seen as "mathematical" in character by many listeners and critics, is what gives the genre its name. It is commonplace to find guitarists in math rock groups using the "tapping" method of guitar playing, and loop pedals are occasionally incorporated, such as in the group Battles. Lyrics are generally not the focus of math rock; the voice is treated as just another sound in the mix.

Source: http://en.wikipedia.org/wiki/Math_rock