African slaves were ancestors of the banjo. While many were pressured to convert to Christianity, the Sahelian slaves were allowed to maintain their musical traditions, adapting their skills to instruments such as the fiddle and guitar. Some were also allowed to perform at balls for slave-holders, allowing the migration of their music across the Deep South. Influence of field hollers Field holler music, also known as Levee Camp Holler music, was an early form of African American music, described in the 19th century. Field hollers laid the foundations for the blues, spirituals, and eventually rhythm and blues. Field hollers, cries and hollers of the slaves and later sharecroppers working in cotton fields, prison chain gangs, railway gangs (Gandy dancers) or turpentine camps were the precursor to the call and response of African American spirituals and gospel music, to jug bands, minstrel shows, stride piano, and ultimately to the blues, rhythm and blues, jazz and African American music in general. Sylviane Diouf and Gerhard Kubik have traced the origins of field hollers to African Muslim slaves, who were influenced by the Islamic musical tradition of West Africa (see African roots above). Influence of spirituals The most important American antecedent of the blues was the spiritual, a form of religious song with its roots in the camp meetings of the Great Awakening of the early 19th century. Spirituals were a passionate song form, that "convey(ed) to listeners the same feeling of rootlessness and misery" as the blues. Spirituals, however, were less specifically concerning the performer, instead about the general loneliness of mankind, and were more figurative than direct in their lyrics. Despite these differences, the two forms are similar enough that they can not be easily separated — many spirituals would probably have been called blues had that word been in wide use at the time. Social and economic aspects The social and economic reasons for the appearance of the blues are not fully known. Blues has evolved from an unaccompanied vocal music of poor black laborers into a wide variety of styles and subgenres, with regional variations across the United States. African American work songs were an important precursor to the modern blues; these included the songs sung by laborers like stevedores and roustabouts, and the field hollers and "shouts" of slaves. The first appearance of the blues is not well defined and is often dated between 1870 and 1900, a