Tracking Song and vizcacha and Virgil

Dave Liebling asks (nine years ago) what we are to make of "Tracking Song's epigraph (http://www.urth.net/urth/archives/v0007/0586.shtml<http://www.urth.net/urth/archives/v0007/0586.shtml>), and I think it is about time he had an answer. Is this another layer of the story? And what about Great Raven?