African slaves often used Christian hymns to communicate. The slaves used these hymns in order to communicate coded messages to each other about their conditions, and possible avenues for escape. The slaves' overseers thought that the slaves were simply singing religious songs and were not able to recognize the messages hidden within these songs. These hymns had an influence on the later musical style of the African American spiritual.
This was done to share hardships and various Christian principles. Most slaves could not read or write so they relied on an oral tradition to pass down stories, religious beliefs, and any other important information. This led to the creation of the musical style that we refer to today as spirituals.