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 and Roll (also known as Rock 'n' Roll), is a genre of music that evolved in the United States in the late 1940s and early 1950s, and quickly spread to the rest of the world. It later spawned the various sub-genres of what is now called simply 'rock music'.