Black metal is an extreme subgenre of heavy metal. It often employs fast tempos, shrieked vocals, highly distorted guitars played with tremolo picking, double-kick drumming, and unconventional song structure.
Indie rock is an umbrella term to reference rock artists that are or were unsigned, or have signed to independent record labels, rather than major record labels. Originally the term was not a reference to a specific genre of rock music; however, it has come to be used often to reference the sound of particular bands and the bands they have influenced. "Indie rock" is used as an umbrella term covering a wide range of artists and styles close to rock music, connected by some degree of allegiance to the values of underground culture and counterculture. Genres or subgenres often associated with indie rock include lo-fi, post-rock, sadcore, C86, and math rock, to list but a few; other related (and sometimes overlapping) categories include shoegazing and indie pop.