Bob Dylan is an American musician, singer-songwriter, artist, and writer. He has been an influential figure in popular music and culture for more than five decades. Much of his most celebrated work dates from the 1960s, when he was an informal chronicler and a seemingly reluctant figurehead of social unrest. A number of Dylan's early songs, such as "Blowin' in the Wind" and "The Times They Are a-Changin'", became anthems for the US civil rights and anti-war movements. Leaving behind his initial base in the culture of the folk music revival, Dylan's six-minute single "Like a Rolling Stone" radically altered the parameters of popular music in 1965. His recordings employing electric instruments attracted denunciation and criticism from others in the folk movement. Dylan's lyrics have incorporated a variety of political, social, philosophical, and literary influences. They defied existing pop music conventions and appealed hugely to the then burgeoning counterculture. Initially inspired by the performance style of Little Richard, and the songwriting of Woody Guthrie, Robert Johnson, and Hank Williams, Dylan has both amplified and personalized musical genres. His recording career, spanning fifty years, has explored many of the traditions in American song—from folk, blues, and country to gospel, rock and roll, and rockabilly to English, Scottish, and Irish folk music, embracing even jazz and swing. Dylan performs with guitar, keyboards, and harmonica. Backed by a changing line-up of musicians, he has toured steadily since the late 1980s on what has been dubbed the Never Ending Tour. His accomplishments as a recording artist and performer have been central to his career, but his greatest contribution is generally considered his songwriting.