Hi, Joe:
Obviously, it sure caught my interest! I've learned a lot from my short search about this. There are several more songs at the Library of Congress "American Memory" site that are similar to the ones I've posted. Not sure where else to look (any suggestions would be appreciated!). But the ones I've seen so far appear to fall into the the following categories:

Songs about how happy the carefree, playful slave is on the plantation (dancing and making music in the evenings; hunting small game; courting and marrying; sneaking off to town to play while "Massa" is away; etc.).

Songs about how miserable the fugitive slaves or the emancipated slaves are (or would be) in their present circumstances and how much they miss their old life as slaves (where Massa cared for them; where they didn't have to take responsibility for their own happiness; etc.).

Songs ridiculing the free blacks (e.g. the aforementioned "Zip Coon" -- I found the lyrics for that one but did not post them because I think they're VERY demeaning -- perhaps I should have posted them for that very reason [to demonstrate just how hateful these songs can be!]).

Songs that are outright warnings (warning blacks against running away or seeking emancipation; warning whites against violent fugitive slaves and freedmen; warning voters against approving abolitionist policy; etc.). By the way, I also found what must be a couple of post-war songs warning white girls not to fall in love with black men, and warning white men not to let their daughters be courted by black men (although they're irrelevant to the "pro-slavery" discussion, they certainly express anti-emancipation sentiment!).

Political campaign songs critical of abolitionist policy in general (and, in the later songs, of the "tyrant" Lincoln in particular). Many if not most of these are pro-Union and pro-Constitution, with the emphasis on an interpretation of "states' rights" that favored the continuation of slaveholding in states that would vote to approve it (ignoring the voting-fraud aspect of that particular scenario, that would skew the results in favor of slaveholding!!).

War songs (pre-Civil War and Civil War) celebrating the cause of states' rights (e.g. the right to own slaves) and celebrating Confederate victories, and including criticism of the North's tyranny and of individual military and political leaders in the North.

Did I miss any categories?

Sharon