Handed down from the days of slavery, work songs helped black field workers pass the time under oppressive social and environmental conditions. They were usually simple, repetitive chants and melodies, easily remembered and modified. Some work songs had a spiritual focus, while others were carefully coded metaphors containing social commentary and/or guidelines for escape. After slavery was abolished, work songs continued to be passed along, especially in black sharecropper families who still worked in the South. The field recordings by the father/son team of John and Alan Lomax, most made during the first half of the 20th century, constitute the primary modern-day source for work songs.