The first two pages of "Sirens" is one of those places where you may want to pull back on the reins of your understanding and just appreciate the language itself. If you like, you can figure out what each line refers to with the help of Gifford's annotations, but the point, generally, is that this is like the tuning of a symphony. "Sirens" is the most musical chapter yet. We have the tap-tap-tap of the blind piano tuner's cane, the constantly jingling carriage of Boylan as he heads to see Molly, as well as the dizzying beautiful language as Bloom's emotions fall in line with Dedalus's singing. At times, the sound of the language can come to dominate the sense. Meaning gets the backseat, and musicality is shifted to the front. Now, this can be aesthetically appealing and beautiful, but as we'll see, it also comes with its dangers.
Now, in Book 12 of the Odyssey, Circe warns Odysseus about the power of the Sirens. Their singing is so beautiful that it drives men mad. She advises him to stop his crew's ears with wax, and to tie himself to the mast. He follows her advice, and because he is constrained he himself gets to hear the Sirens beautiful singing while passing safely by their isle.
Joyce's schema lists the two barmaids, Lydia Douce and Mina Kennedy, as the Sirens. You probably noticed that the men in the bar do seem quite allured with the two women. First, Miss Douce catches a man in the viceregal cavalcade looking in at her, then Simon Dedalus comes in and flirts with her, then Boylan does the same, then George Lidwell. But the danger of the Sirens in this chapter is broader than the sexual appeal of the barmaids, or even the beauty of the music that Dedalus, Cowley, and Dollard start playing at the piano. The big risk here is falling into sentimentality.
As Bloom eats his dinner with Richie Goulding, he listens to Simon Dedalus sing from Martha and feels his emotions become guided along by the music. Later, when Ben Dollard sings "The Croppy Boy," the entire bar becomes emotional. The music, though beautiful, can also make one feel melodramatic, feeling intense emotions that may or may not be justified by the situation. At this point, Bloom knows that Blazes Boylan is on his way to sleep with Molly at Eccles Street, and letting his emotions get out of hand is a real threat. He can't help but associate his own tragic situation with that of "The Croppy Boy."
So, who is "The Croppy Boy" anyway? The song is a famous one about the fate of Robert Emmet. Emmet was an Irish patriot that tried to get Napoleon's assistance for an Irish uprising. In 1803, he led an attempt to seize the Dublin castle, but neither Napoleon nor his Irish allies supported him. What was supposed to be a revolt turned into a riot, and the Lord Chief Justice was piked (to be run through with a pike) to death. Emmet promptly went into exile, but was eventually found out. The legend is that he came back to say goodbye to his fiancée, and when he went to confession, the priest turned out to be a British soldier in disguise. Emmet was hanged and beheaded in a public execution that went horribly wrong. With time, he became a popular mythic Irish figure, part of the nation's infatuation with the idea of tragic but ennobled failure.
Bloom cuts out early so as to avoid the morose end of the song, but then he sees Emmet's picture hanging in an antique window in the street. As Bloom lets out the fart that's been building inside of him ever since he left the Ormond Hotel, he thinks of Emmet's famous last words: "When my country takes her place among the nations of the earth then and not till then, let my epitaph be written. I have done" (11.619-25). The fact that Joyce breaks the words up with the sounds of Bloom's fart would have been scandalous to many Irish people at the time who still worshipped Emmet. Part of the point of the juxtaposition is to pull down something that the Irish people hold sacred. It reveals how certain words – no matter how brave – can become sentimentalized when repeated over and over again. Joyce was very aware of how the Irish people could become imprisoned in their own myths, constantly holding up the past and disparaging the present. The point here is that if the myth isn't made new and relevant, then perhaps it's not worth anything more than a fart.
Plot wise, this is more or less the moment of truth for Bloom. The other two times he has seen Boylan today (from the carriage in "Hades" and outside the National Library in "Lestrygonians"), he has avoided him. Here, as the hour of the affair draws near, Bloom decides to follow Boylan into the Ormond Hotel. But once inside, he's still passive. He doesn't speak to him, and when Boylan gets up to leave, Bloom says nothing, though he gasps with anxiety. From one point of view, Bloom may look like a coward, but he has also brought himself as close as he can to what is going to happen instead of avoiding it once again.
There's a line that you'll hear about Ulysses if you spend more time with it. It comes from Hamlet, but it's used in a different sense here: "The play's the thing." In this chapter, more than any other up to this point, we see Joyce playing with words as if they were toys. For instance:
"Miss Kennedy sauntered sadly from bright light, twining a loose hair behind an ear. Sauntering sadly, gold no more, she twisted twined a hair. Sadly she twined in sauntering gold hair behind a curving ear" (11.72).
Joyce was also interested in the sense of words, how often buried connotations of a word could change the entire meaning of a passage, but here it's much more about the sound and the style. It's like Dr. Seuss, except with every word in the English language at his disposal. The best way to read these lines may be to think of the author smiling broadly to himself, turning phrases round and round as he works to keep himself entertained, getting drunk on his own words and images.