The blues is a vocal and instrumental form of music based on a pentatonic scale and a characteristic twelve-bar chord progression. The form evolved in the United States in the communities of former African slaves from spirituals, praise songs, field hollers, shouts, and chants. The use of blue notes and the prominence of call-and-response patterns in the music and lyrics are indicative of the blues' West African pedigree. The blues has been a major influence on later American and Western popular music, finding expression in ragtime, jazz, bluegrass, rhythm and blues, rock and roll, hip-hop, and country music, as well as conventional pop songs.
The phrase the blues is a synonym for having a fit of the blue devils, meaning low spirits, depression and sadness. An early reference to this can be found in George Colman's farce Blue devils, a farce in one act (1798). Later during the 19th century, the phrase was used as a euphemism for delirium tremens and the police. Though usage of the phrase in African American music may be older, it has been attested to since 1912 in Memphis, Tennessee with W. C. Handy's "Memphis Blues".In lyrics the phrase is often used to describe a depressed mood.
There are few characteristics common to all blues, because the genre takes its shape from the peculiarities of individual performances. However, some characteristics have been present since before the creation of the modern blues and are common to most styles of African American music. The earliest blues-like music was a "functional expression, rendered in a call-and-response style without accompaniment or harmony and unbounded by the formality of any particular musical structure." This pre-blues music was adapted from slave field shouts and hollers, expanded into "simple solo songs laden with emotional content". The blues, as it is now known, can be seen as a musical style based on both European harmonic structure and the West African call-and-response tradition, transformed into an interplay of voice and guitar.
Many blues elements, such as the call-and-response format and the use of blue notes, can be traced back to the music of Africa. Sylviane Diouf has pointed to several specific traits—such as the use of melisma and a wavy, nasal intonation—that suggest a connection between the music of West and Central Africa and blues. Ethnomusicologist Gerhard Kubik may have been the first to contend that certain elements of the blues have roots in the Islamic music of West and Central Africa.
Stringed instruments (which were favored by slaves from Muslim regions of Africa…), were generally allowed because slave owners considered them akin to European instruments like the violin. So slaves who managed to cobble together a banjo or other instrument…could play more widely in public. This solo-oriented slave music featured elements of an Arabic-Islamic song style that had been imprinted by centuries of Islam's presence in West Africa, says Gerhard Kubik, an ethnomusicology professor at the University of Mainz in Germany who has written the most comprehensive book on Africa's connection to blues music (Africa and the Blues).
Kubik also pointed out that the Mississippi technique of playing the guitar using a knife blade, recorded by W.C. Handy in his autobiography, is common to West and Central Africa cultures where the kora, a guitar-like instrument, is often the stringed instrument of choice. This technique consists of pressing a knife against the strings of the guitar, and is a possible antecedent of the slide guitar technique.
Robert Johnson, a Delta blues singer, is generally considered responsible for the standardization of the 12-bar blues.Blues music later adopted elements from the "Ethiopian airs"—"Ethiopian" is used here to mean "black"—of minstrel shows and Negro spirituals, including instrumental and harmonic accompaniment. The style also was closely related to ragtime, which developed at about the same time, though the blues better preserved "the original melodic patterns of African music". Songs from this early period had many different structures. Examples can be found in Leadbelly's or Henry Thomas's recordings. However, the twelve-, eight-, or sixteen-bar structure based on tonic, subdominant and dominant chords became the most common. What is now recognizable as the standard 12-bar blues form is documented from oral history and sheet music appearing in African American communities throughout the region along the lower Mississippi River during the first decade of the 1900s (and performed by white bands in New Orleans at least since 1908). One of these early sites of blues evolution was along Beale Street in Memphis, Tennessee.