The speaker is talking about a night job, and the title, "Graveyard shift," points that way. The opening is flat and almost shrugging: work is just a way to get money. Even that comes with a limit. They want enough to live on, but not so much that their "pretty hands" are damaged, which sounds half joking and half protective of the body and self that labor can wear down.
Then the tone turns sharper and more desperate. The speaker asks to have their head drilled open, a trepanning, because it is full of "bad music," a phrase that suggests a nagging, unwelcome noise in the mind, perhaps exhaustion or dark thoughts. The last lines widen the wish: pierce the night itself and let "the plague" out.
The mood is weary, restless, and a little grim, with dry humor running underneath. Night work seems to leave the speaker feeling sick or trapped, and they long for release.