Some of the songs had secret messages in them that the slaves would use in order to communicate. They used the secret messages in the songs to plan rebellions. 

Songs such as "Steal Away" or "Swing Low, Sweet Chariot" were sung at night and the indicated that it was time to escape. 

Whenever a song contained some river such as the Mississippi or Ohio River, that meant that the slaves would have to cross some kind of body of water to escape. 

The song "Wade in the Water" had specific instrunctions that the fugitive slaves had to follow in order to successfully escape and not get caught. 

"The Gospel Train" and "Follow the Drinking Gourd" included lyrics that gave detailed descriptions on how to get to an underground railroad. 

The runaway slaves would often go into the water instead of going on land.