I recently finished reading Suzanne Collins' The Ballad of Songbirds and Snakes for the first time. Here are some small observations.
In chapter six, the narrator explains that "Everybody called him [Pliny Harrington] Pup to differentiate him from his naval commander father" (p. 91). The combination of Pliny Harrington, Sr. and Pliny Harrington, Jr. seems to be a nod to Pliny the Elder and Pliny the Younger.
Bridging chapters twenty-four and twenty-five, the Covey experiences a tense encounter with Billy Taupe. As Coriolanus sizes him up, the narrator explains that "over one shoulder hung a boxy instrument with part of a piano keyboard along one side" (p. 368). Shortly after this, Coriolanus again glimpses Billy Taupe who is accompanied by "a soft, mechanical wheeze," and the narrator notes that "his instrument [was] the source of the wheeze" (p. 373). Apparently, his instrument is an accordion. Since the accordion is a reed instrument, it contrasts with the stringed instruments that the rest of the Covey play (mandolin, fiddle, bass, and guitar, listed on page 361), and the difference between these instrument families highlights the rift that exists between Billy Taupe and the rest of the Covey.
The main character is called Coriolanus for most of the book, but in the epilogue, he's referred to merely as Snow. This change seems to indicate that after his experience with the Hunger Games and his time in the Peacekeepers, he's become more impersonal and withdrawn. This is hinted at near the end of chapter thirty, where he's glad that the snake bite he received while chasing after Lucy Gray will probably leave a scar because he thinks that "it will remind me to be more careful" in his relationships (p. 506). His concern for his family legacy, which appears throughout the book, probably contributes to this shift, too.
