I have done some amateur research on this over the years, helped much by some information I received decades ago from James Cone (I was a mere babe at the time of course :>). There was, as we know, a set of symbols and euphimisms which slaves used to faciliate escape and connection with the underground railroad. One was sung by a house slave, and led with "can't hear nobody pray," which suggested that everybody in the house was asleep. "steal away" (a song attributed to Nat Turner by some), was supposed to waft through the air as someone came to guide the slaves away from where they lived. Of course, "Wade in the Water" was a teaching song ("God's gonna trouble the water" mean that it was harder for dogs to track, and "Drinking Gourd" was a song specifically about instructions on escape from either Alabama or Mississippi: "When the sun comes back and the first quail calls", for instance, refers to early spring). I'm always looking for other such songs. Songs referencing Moses refer to Harriet Tubman, of course, and references to chariots, trains, etc. reference the UR. Also, the Jordan River was alternately the Ohio or the St, Lawrence River (depending on before or after the fugitive slave law was enacted). I have maybe 10-12 songs that may apply.