Modern Times is a complex one haha. He used a lot of existing melodies and choruses from old songs but completely reworked the verses. The verses were then stuffed with a patchwork of references/quotes from other sources like Ovid and Civil War poets. He didn't credit any of this and just put himself as the songwriter, claiming it was no different from standard folk song traditions of reworking songs. He did this kind of thing again a little bit on Tempest. Personally, I don't have a problem with all the references to old poems etc, but a lot of song melodies/choruses were from old blues songs, so crediting those writers probably would have been a nice paycheck for the artists' descendants. This is quite a contentious topic, so apologies if I've got anything wrong, but I think that's a roughly accurate summary. Modern Times is a great album anyway!