Then by the bed-side, where the faded moon Made a dim, silver twilight, soft he set A table, and, half-anguish'd, threw thereon A cloth of woven crimson, gold, and jet;— O for some drowsy Morphean amulet! The boisterous, midnight, festive clarion, The kettle-drum, and far-heard clarionet, Affray his ears, though but in dying tone:— The hall door shuts again, and all the noise is gone.
What do you do once you've crept up to the bedside of your mostly unconscious girlfriend? You make her a picnic, that's what.
A "Morphean amulet" is a sleep charm, referring to Morpheus, the Greek god of sleep and, even more importantly, dreams.
Madeline is (as far as Porphyro can tell, anyway) asleep, so why's Porphyro hankering for a sleeping charm?
Two options: it could be for Madeline because he's afraid she's going to wake up when the music bursts in.
Otherwise, it could be for himself: the plot so far has been following Porphyro as he successfully penetrates each layer of space between him and Madeline. He got into the castle, he got into her bedroom, he's gotten into her bed, and now he's going to get into her dream world too. Porphyro: not great with the concept of personal space.
In the last few lines, somebody's opened a door, and the music from the rager downstairs (yes, it's still going on—never say these people don't know how to party) fills the room and freaks Porphyro out for a second before the door's shut and the music disappears.
Once again we're in total silence (and we start to sense an emerging pattern where music is consistently mentioned and then repressed).