First emerging from within African-American communities of the Mississippi Delta during the late 19th century, the blues has come to typify both its own musical form and music genre. Evolved from spirituals, work songs, narrative ballads, and ancient chants, the blues is identified by specific chord progressions, typically expressed by a twelve-bar chord progression and sung in a flat minor to major third 3-on-tone scale. As a genre, the blues is based on the blues form and other traits including specific instruments and lyric tone. Most often, blues music is characterized by the song's melancholy and sadness and often depict tales of heartbreak, solemn memories, nostalgia, loss, and unfulfilled dreams. Some of the best known sub-genres of the blues include Delta, Jump, Piedmont and Chicago blues styles. Throughout time, the blues has influenced the development of many other music styles including bluegrass, rock and roll, rhythm and blues, pop and hip hop.