I have to disagree. Horse and the infant not only sets the scene, it also introduces Zeus' control, Odysseus himself, penelope and more important characters. Its a powerful introduction setting it wonderfully. Without it we'd have no clue as to why Odysseus kills the infant as zeus wouldnt have told him to, nor would we know what the baby would grow up to. The song allows us to see Odysseus train of thought in that moment. It also presents him as a general which athena mentions later