The Piano Lesson is in many ways a straight-up ghost story. The Charles family is being haunted by the ghost of Sutter, whose family once owned theirs. Of course, the Charles family has a few ghosts on their side as well. First, there are the Ghosts of the Yellow Dog, who may well have killed Sutter in the first place. At the play's climax, the Ghosts of Yellow Dog return and, with the help of the spirits of the Charles family's ancestors, give Sutter's ghost the boot. All these literal ghosts haunting the play also have a symbolic meaning. The battle that happens between the ghost of Sutter and the African-American ghosts seems to represent the struggle for racial equality that blacks faced in the time of slavery and today.
Though Crawley isn't depicted as a literal ghost, he haunts Berniece just the same.
Sutter's ghost is symbolic of America's shameful history of slavery.