I'm not sure about the phrase : It grinds smoothly I think that they refers to grind seed (coffe , wheat) I don't know about this story but here you have an idea about .

*Cumbia is one of the Latin Dance music style. Cumbia is to Columbia what samba is to Brazil,

* Mi Tierra : it's a way to call where you were born (city, country, in this case Colombia )

*Chambacu : was a neighborhood of Cartagena (Colombia), located on the outskirts of the historic city center, and disappeared in 1971. Considered the largest slum in the country.