I was lookig up lyrics to "Down in the River to Pray" and the Wikipedia page claims that some historians believe that larts of the hymn were coded messages with advice to escape. This is something I have heard all my life about this type of song from many different people, but the claims seem a bit far-fetched. For example, all of the "codes" are always either really obvious advice like "go through the river to cover your scent" or "use stars for navigation" or things which seem too specific to be a widely understood secret code.

In the above example, it is claimed that "going down in the river to pray" was advice to go through the water. The same is said about the hymn "Wade in the Water" (though for that one it seems a bit more likely to me). "Swing Low Sweet Chariot" is often said to refer to the underground railroad in the phrase

*I looked over Jordan and what did I see? (Coming for to carry me home) A band of angels coming after me (Coming for to carry me home)

Anyway, my question is this- is there any evidence of these songs actually being a code? If so, how would slaves have known about the code, and are there notable instances of slave escapes which were inspired/aided by these? If not, how did this myth become so widely circulated?