There has always been "popular" music in the United States, and all forms of music are popular with certain audiences. The term "pop music," though, generally refers to styles of music that are nonclassical, mainstream, intended for very wide audiences. Pop music is often controlled by large music companies. In the early decades of the twentieth century, these large companies were sheet-music publishers. After 1930, the large music companies controlling the release of pop music were the recording companies. Pop music is usually music meant to turn a profit. That does not mean pop music is not good music. Throughout the twentieth century, pop music has provided some of the greatest music of all time.

Because pop music is meant to sell records, music companies have constantly been on the lookout for the next big song. Thus, pop music is in many ways a history of one...