Bonta's speaker wakes on a rainy day with an urge to move that the weather won't allow. His shoes look like open graves, and the rain on the roof sets up a rhythm he can almost feel in his body. The restlessness has no clear cause, and he knows it.
The central image is the mussel in his chest, a shellfish that opens and grips the riverbed with its foot so it can sway in the current. He is both anchored and longing to flow. From there his wishes widen: to follow the river toward the sky, to have the horizon stop retreating, to see forests take back the fields, and to find a woman whose eyes are dark as earth.
The mood is wistful and a little weary, like the blues in the title. Underneath it runs a desire to leave human clutter behind and belong to something older and more natural.