Hard Rock/Heavy Metal  is a form of loud, aggressive rock music. The electric guitar is often emphasised, used with distortion and other effects, both as a rhythm instrument using repetitive riffs with a varying degree of complexity, and as a solo lead instrument. Drumming characteristically focuses on driving rhythms, strong bass drum and a backbeat on snare, sometimes using cymbals for emphasis. The bass guitar works in conjunction with the drums, occasionally playing riffs, but usually providing a backing for the rhythm and lead guitars.Vocals are often growling,