When did the slaves sing?

Slaves sung before during and after their work as slaves. They sung before they began work to build up their energy and strength to push them on so that they could work with strength. They sung while working to pass time to keep their mind preoccupied. They sung after work to pass time as well as to worship their God. They sung as they were walking so that they could feel strong. They sung so that they could get through their rough and tiring days.