Rock music is a form of popular music with a prominent vocal melody accompanied
by guitar, drums, and bass. Many styles of rock music also use keyboard
instruments such as organ, piano, mellotron, and synthesizers. Rock music
usually has a strong back beat, and often revolves around the guitar, either
solid electric, hollow electric, or acoustic.
Many rock bands consist of a guitarist, lead singer, bass
guitarist, and drummer, forming a quartet. Some groups omit one or more of these
roles and/or utilize a lead singer who plays an instrument while singing,
forming a trio or duo; others include additional musicians such as one or two
rhythm guitarists and/or a keyboardist. More rarely, groups also utilize
stringed instruments such as violins or cellos, and/or horns like trumpets or
trombones.
Rock music has its roots in 1940s and 1950s rock and roll and
rockabilly, which evolved from blues, country music and
other influences. According to the All Music Guide, "In its purest form, Rock
& Roll has three chords, a strong, insistent back beat, and a catchy melody.
Early rock & roll drew from a variety of sources, primarily blues, R&B,
and country, but
also gospel, traditional pop, jazz and folk. All
of these influences combined in a simple, blues-based song structure that was
fast, danceable, and catchy."
In the late 1960s, rock music was blended with folk music to
create folk rock, blues to create blues-rock and with jazz, to create jazz-rock fusion,
and without a time signature to create psychedelic rock. In the 1970s, rock
incorporated influences from soul, funk, and latin music. Also in the 1970s,
rock developed a number of subgenres, such as soft rock, heavy metal, hard rock,
progressive rock, and punk rock. Rock subgenres that emerged in the 1980s
included synth-rock, hardcore punk and alternative rock. In
the 1990s, rock subgenres included grunge, Britpop, indie rock, and nu metal.
