Dave Bonta's short poem pictures a swan alone, getting weaker, and imagining music that is already finished. The title points to an old idea: that a swan, silent for most of its life, sings one beautiful song just before it dies. Here, though, the song never really arrives. The swan doesn't sing at all. It only dreams of "dead tunes," melodies that belong to the past.
The mood is quiet and sad. The word "alone" sits at the start, and "sickly" makes the swan seem frail, while "dead tunes" suggests that whatever music it has left is already gone. There's no drama or complaint in the voice. The speaker simply watches and reports, which makes the loneliness feel heavier. You might read the swan as a stand-in for anyone, perhaps an artist, whose creative voice is fading. The poem doesn't say so outright, but its few words leave room for that reading.