House is a music genre characterized by a repetitive four-on-the-floor beat and a typical tempo of 120 beats per minute. It was created by DJs and music producers from Chicago's underground club culture in the late 1970s, as DJs began altering disco songs to give them a more mechanical beat. House was pioneered by DJs and producers in Chicago such as Frankie Knuckles, Ron Hardy, Jesse Saunders, Chip E., Steve "Silk" Hurley, Farley "Jackmaster" Funk, Marshall Jefferson, Phuture, and others. House music expanded to other American cities such as New York City and became a worldwide phenomenon.