In Book 8 of the Odyssey, what does the blind poet Demodocus' presence and his singing do for the story?
In book eight of the epic poem The Odyssey, the blind bard Demodacus serves as a catalyst to reveal Odysseus's identity to the Phaeacians.
In his journey back to his home in Ithaca, Odysseus encounters the Phaeacians. With a little help from his patron goddess, Athena, he is disguised and presented to the King and Queen. They receive him kindly but don't know who he is. King Alcinous prepares a feast with a celebration of games for the visitor's arrival. Demodacus is called in to provide entertainment, and he begins to sing of the dispute between Odysseus and Achilles. This is a clever way to deliver some of Odysseus's backstory. When Odysseus hears this, he is moved to tears and tries to hide this from his Phaeacian hosts. Upon seeing this, Broadsea goads him and he is once more given a chance to prove his bravery and strength.
The second song that Demodocus sings is about the love between Ares and Aphrodite, and it parallels the love that Princess Nausicaa of the Phaeacians is beginning to feel for Odysseus. Again, this is a clever way to reveal the next woman who becomes besotted with Odysseus.
The third song Demodacus sings is about the Trojan War, and it is when Odysseus reveals his identity to his hosts. This is how Demodacus becomes the catalyst for the revealing of Odysseus' identity.
Although some scholars have surmised that the blind bard in book eight is a depiction of Homer himself, it is difficult to prove this to be true. Very little is known about Homer's life. We do, however, know that storytelling through the oral tradition was a big part of the pre-literate society in which Homer lived.
Demodocus's first song, the one concerning Odysseus and Achilles's disagreement at Troy, serves a useful function in the poem, namely to provide information about Odysseus's character and background. At this point in The Odyssey, Odysseus is the guest of the Phaeacians, his true identity unknown. Demodocus also doesn't know who this strange guest is, and in any case being blind wouldn't be able to identify him. It's this blissful ignorance of Odysseus's true identity that gives Demodocus's song its air of authenticity. The blind bard has no reason to lie, or embellish Odysseus's disagreement with Achilles in any way. His song, and the events it relates, has the ring of truth about it.
More important still is Demodocus's third song, one that relates to the Trojan horse and the sack of Troy. Again, Demodocus is providing us with some useful background detail about Odysseus. This helps to set the scene for what's about to follow, when a visibly emotional Odysseus is prompted by King Alcinous to reveal his true identity, and to tell his story to the assembled guests.
The blind bard is very important to Homer's tale for several reasons. First, many researchers and readers alike believe the bard is supposed to represent Homer himself and his role in the society of the times. It is believed he was a blind bard, making a living by singing of the trials and tribulations of the upper class citizens.
To Book 8 however, he is important because of Odysseus' response to his song. Note Odysseus offers food and drink to the bard and is moved to tears by his songs of the Trojan War and of Odysseus' journey. Remember a King or person of Odysseus' status would not normally offer food or thanks to a bard. This emotional display on the part of Odysseus is what allows Alcinous to prod him for revelation of his identity, which in itself is a large reocurring theme in The Odyssey. So, the bard is a catalyst for major events in the book.
The poet's presence does several things. It gives Homer a chance to remind listeners to his poem of the backstory--the history that had gone before, which was included in his Iliad. By putting a blind bard in, he may be commenting on himself, and even giving listeners a chance to reflect on his quality by comparing it to the summary given here. (It also functions as a kind of advertising, if that isn't too crude.) Finally, it humanizes Odysseus. He cries when he hears this, making him much deeper emotionally than the pure hero he had been.