Symbolism, Imagery, Allegory
For McCullers, hands are more than just useful hook-substitutes at the end of your arms. They seem to demonstrate a person's interactions with others—the way one body does (or does not) reach out and touch another. They express themselves in a way that their owners' mouths can't… or won't.
Here's one such example, when we meet Cousin Lymon for the first time: "His hands were like dirty sparrow claws and they were trembling," (Ballad.22). With this description, the narrator encourages an image of a wild beggar, cold and scared, even as Lymon swaggers around confidently—as if hands are the ultimate truth-tellers. His hands show an edge of sadness and desperation, which seems to evaporate as Lymon becomes beloved.
It's no surprise that hands crop up often in "Wunderkind," the story of a piano player. In the first moments, before we know much about Frances, we see her hands:
As she jerked off her mittens she saw that her fingers were twitching to the motions of the fugue she had practiced that morning. (Wunderkind.3)
By way of Frances's hands, and her own gaze, we learn about her desperation, too. It's very different from Lymon's (and not as intense) but it too is carried in the hands.
Neither Cousin Lymon nor Frances ever vocally expresses this desperation: it seems like their hands must carry it until an action, (like dashing out the door, or doing an attention-grabbing jig to the point of falling over) broadcasts it loud and clear.