In which category of music would you find a song typically sung while working?

ethnic
popular
folk
art

Folk song.

Explanation:

The tradition of singing while working has been a common theme in almost all of the world's people. Majority of the manual workers, especially in the past, sing along as a means of entertainment and instilling confidence in themselves through their songs. Likewise, the slaves in the plantations also use songs as a means of expressing themselves. These form of songs are typically known and referred as folk songs, which embodies the traditional and sometimes even the personal issues of their times.

this is a good question! i'll do some research and come back when i have the answer!

i believe their role is to instruct certain sections on when they are to join and when they are to stop