Math rock is a very loosely defined genre of music. The term is hard to describe and often misused. However, one good way to describe it is as a style of rock that has almost no trace of folk or blues, which is the traditional definition of rock. Instead, the sound may have a loose, jazzy-like and spontaneous feeling, in contrast to the direct and compelling sound of blues and folk. At the same time however, the music is also calculated, and instrumental riffs are often based on timed formulas. For example, a guitar riff may repeat a sequence of five quarter-notes over 4/4 time signature, thus giving the listener an overall feeling of chaos, in spite of the riffs rigid structure.
The genre is gaining more influence, especially in the Los Angeles area. Bands like The Blood Brothers, Plot to Blow Up the Eiffel Tower, and An Albatross are some of the most famous math rock bands.