Country music often consists of ballads and dance tunes with generally simple forms, folk lyrics, and harmonies accompanied by mostly string instruments such as banjos, electric and acoustic guitars, steel guitars (such as pedal steels and dobros), and fiddles as well as harmonicas. Blues modes have been used extensively throughout its recorded history.
According to Lindsey Starnes, the term country music gained popularity in the 1940s in preference to the earlier term hillbilly music; it came to encompass Western music, which evolved parallel to hillbilly music from similar roots, in the mid-20th century. In 2009 in the United States, country music was the most listened to rush hour radio genre during the evening commute, and second most popular in the morning commute.
The term country music is used today to describe many styles and subgenres. The origins of country music are the folk music of working class Americans, who blended popular songs, Irish and Celtic fiddle tunes, traditional English ballads, cowboy songs, and various musical traditions from European immigrants.
Immigrants to the southern Appalachian Mountains of eastern North America brought the music and instruments of Europe along with them for nearly 300 years. Country music was "introduced to the world as a Southern phenomenon."
The U.S. Congress has formally recognized Bristol, Tennessee as the "Birthplace of Country Music", based on the historic Bristol recording sessions of 1927. Since 2014, the city has been home to the Birthplace of Country Music Museum. Historians have also noted the influence of the less-known Johnson City sessions of 1928 and 1929, and the Knoxville sessions of 1929 and 1930. In addition, the Mountain City Fiddlers Convention, held in 1925, helped to inspire modern country music. Before these, pioneer settlers, in the Great Smoky Mountains region, had developed a rich musical heritage.
The first generation emerged in the early 1920s, with Atlanta's music scene playing a major role in launching country's earliest recording artists. New York City record label Okeh Records began issuing hillbilly music records by Fiddlin' John Carson as early as 1923, followed by Columbia Records (series 15000D "Old Familiar Tunes") (Samantha Bumgarner) in 1924, and RCA Victor Records in 1927 with the first famous pioneers of the genre Jimmie Rodgers) and the first family of country music The Carter Family. Many "hillbilly" musicians, such as Cliff Carlisle, recorded blues songs throughout the 1920s.
During the second generation (1930s–1940s), radio became a popular source of entertainment, and "barn dance" shows featuring country music were started all over the South, as far north as Chicago, and as far west as California. The most important was the Grand Ole Opry, aired starting in 1925 by WSM in Nashville and continuing to the present day. During the 1930s and 1940s, cowboy songs, or Western music, which had been recorded since the 1920s, were popularized by films made in Hollywood. Bob Wills was another country musician from the Lower Great Plains who had become very popular as the leader of a "hot string band," and who also appeared in Hollywood westerns. His mix of country and jazz, which started out as dance hall music, would become known as Western swing. Wills was one of the first country musicians known to have added an electric guitar to his band, in 1938. Country musicians began recording boogie in 1939, shortly after it had been played at Carnegie Hall, when Johnny Barfield recorded "Boogie Woogie".