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, or synthesizers. Rock music usually has a strong back beat, and often revolves around guitar, either electric or acoustic.
Rock music has its roots in 1950s-era rock and roll and rockabilly. 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, hard rock, progressive rock, and punk rock. Rock subgenres from the 1980s included synth-rock, hardcore punk and alternative rock. In the 1990s, rock subgenres included grunge-style rock, britpop, indie rock, piano rock, and nu metal.