A work song is a piece of music closely connected to a form of work, either sung while conducting a task (usually to coordinate timing) or a song linked to a task that might be a connected narrative, description, or protest song. An example is "I've Been Working on the Railroad". Records of work songs are as old as historical records, and anthropological evidence suggests that most agrarian societies tend to have them. Most modern commentators on work songs have included both songs sung while working as well as songs about work since the two categories are seen as interconnected. Norm Cohen divided collected work songs into domestic, agricultural or pastoral, sea shanties, African-American work songs, songs and chants of direction, and street cries. Ted Gioia further divided agricultural and pastoral songs into hunting, cultivation and herding songs, and highlighted the industrial or proto-industrial songs of cloth workers (see Waulking song), factory workers, seamen, longshoremen, mechanics, plumbers, electricians, lumberjacks, cowboys and miners. He also added prisoner songs and modern work songs. In societies without mechanical time keeping, songs of mobilisation, calling members of a community together for a collective task, were extremely important. Both hunting and the keeping of livestock tended to involve small groups or individuals, usually boys and young men, away from the centers of settlement and with long hours to pass. As a result, these activities have tended to produce long narrative songs, often sung individually, which might dwell on the themes of pastoral activity or animals, designed to pass the time in the tedium of work. Hunting songs, such as those of the Mbuti of the Congo, often incorporated distinctive whistles and yodels so that hunters could identify each other's locations and those of their prey. Most agricultural work songs were rhythmic a cappella songs intended to increase productivity while reducing feelings of boredom.