Country music is primarily a fusion of African American blues and spirituals with Appalachian folk music, adapted for pop audiences and popularized beginning in the 1920s. The origins of country are in rural Southern folk music, which was primarily Irish and British, with African and continental European musics. Anglo-Celtic tunes, dance music, and balladry were the earliest predecessors of modern country, then known as "hillbilly music". Early hillbilly also borrowed elements of the blues and drew upon more aspects of 19th-century pop songs as hillbilly music evolved into a commercial genre eventually known as "country and western" and then simply "country". The earliest country instrumentation revolved around the European-derived fiddle and the African-derived banjo, with the guitar later added. String instruments like the ukulele and steel guitar became commonplace due to the popularity of Hawaiian musical groups in the early 20th century.