Many of these songs are performed without instrumentation, the words being more important than anything else. Steel drums were sometimes used as an accompaniment, this being the traditional sound of the Caribbean. Some performers brought this form of gospel into the main stream with the popular Reggae sound, while still others were recorded during the civil rights movement of the 1960s.
Blues music sprang quite directly from these old songs, although Blues was more secular in nature. The old songs were almost always Christian on their face, but they contained within them codes that were known among the slaves. Some of these codes dated back to old Pagan belief systems, while others were direct connections to individuals or directions on the underground railroad, which was a system of travel that brought people from the slave states into the north.
Probably the best known song in this genre is Swing Low, Sweet Chariot. The song was first recorded in 1909, but the origin goes back to at least the 1860s. Some believe the chariot was a reference to the underground railroad, others attribute it to Biblical scripture, while others say it goes back to the notion that the gods carried spirits from the human realm on a chariot.
The concept of the chariot being an other-worldly mode of transportation from one realm to another crossed many lines from north Africa and Egypt, to Greece and Rome. Basically, in human history, nearly all people had ancestors who embraced this concept. This could be why the song speaks to people on such a personal level, being a sort of archetype that everyone is familiar with.
There were definite scriptural references in Swing Low, Sweet Chariot, especially to the river Jordan. However, it is widely understood that this was code for either the Mississippi or the Ohio Rivers, either of which could be crossed into freedom. It is probable that all histories are true, considering the frequency with which codes were used on the underground railroad.
There are several lesser known songs which referred to the Ohio or Mississippi rivers. The song Follow The Drinking Gourd was specifically a reference to the Big Dipper, which told slaves how to find their way north to freedom. Literacy was nonexistent in the life of a slave, and these songs were a way to teach each other, as well as the next generation, how to become free.
Not matter race, the history of Negro spiritual songs is a fascinating aspect of the human experience which is worthy of study. The way that these songs were utilized to educate and inform one another speaks to an amazing will to thrive. Even in the most desperate of circumstances, people will always come together to fight an oppressor.