When asked to define jazz, both Louis Armstrong and Duke Ellington independently responded by stating that the only real dividing line between music is "good or bad." Jazz is the good kind of music. Birthed in New Orleans and nurtured by practically every region of the United States and the globe, jazz originally combined African rhythm, European harmony, the blues, American melodies and more into a music that moves the feet, satisfies the soul and feeds the mind. Armstrong, an improvisational genius who may be the single most influential popular artist of the 20th century, defines the solo virtuoso in jazz, while Ellington stands as the quintessential bandleader/composer who balanced group interplay and personal expression. Jazz informed the swing era, the smaller bop groups and vocal stars of the 1950s and '60s, Latin and global jazz, '70s fusion, European improvisation, various avant-garde scenes, modern neo-bop and more. Often high-mindedly called "America's classical music," jazz has actually fed most forms of popular music, from R&B to rock to electronic to hip-hop, even as it has increasingly been viewed as art music that is too often separated from the mass marketplace.