Nu metal is a subgenre of alternative metal that combines elements of heavy metal music with elements of other music genres such as hip hop, alternative rock, funk, industrial and grunge. Nu metal bands have drawn elements and influences from a variety of musical styles, including multiple genres of heavy metal. Nu metal rarely features guitar solos; the genre is heavily syncopated and based on guitar riffs. Many nu metal guitarists use seven-string guitars that are down-tuned to play a heavier sound. DJs are occasionally featured in nu metal to provide instrumentation such as sampling, turntable scratching and electronic backgrounds. Vocal styles in nu metal include singing, rapping, screaming and growling. Nu metal is one of the key genres of the new wave of American heavy metal.