In both The Piano Lesson and Hamlet the authors use a ghost as a dramatic device for several reasons. How are the ghosts significant in developing the theme of each play? How are the ghosts' presences used to stimulate the audience's interest in the play's plot. How do the ghosts provide the necessary exposition so that the audience can understand the rest of the story?
In both Shakespeare's play Hamlet and August Wilson's play The Piano Lesson, the ghosts in the stories serve to develop the theme of being released from the past.
In Hamlet, the ghost of Hamlet's father appears before Hamlet to explain the cause of his death and to beg Hamlet to promise he will avenge his father's death. The ghost tells a grim story of his brother, now King Claudius, murdering him while he slept. Claudius then married Hamlet's mother, Gertrude, to take King Hamlet's place on the throne. In addition, the ghost makes it known that he was murdered before he could ask forgiveness for his own sins and is now suffering in hell.
The ghost's story makes Hamlet feels duty-bound to avenge his father's death by killing his uncle. Yet, at the same time, he fears the consequences of committing a murder, especially if he is uncertain of his uncle's true guilt, as we see when, immediately after the ghost of his father departs, he asks himself, "And shall I couple hell?," meaning, should he call forth the powers of hell also (I.v.93). In other words, he's asking himself if he should burn in hell, just like his father, for murdering his uncle. Hamlet's promise to avenge his father and his fear of consequences help drive the plot of the play forward. Plus, it is the story the ghost of King Hamlet tells that makes Hamlet feel torn between duty and fear; therefore, the ghost also helps drive the plot forward.
Similarly, in The Piano Lesson, the ghost of Old Man Sutter makes appearances after having died three weeks earlier when he fell down a well. Old Man Sutter is the grandson of Robert Sutter, who owned the Charleses as slaves, and his appearance symbolizes the Charleses ties to their past, more specifically, to their ties to slavery.
It is believed that Old Man Sutter was pushed down the well to his death by the ghost of Boy Willie, Robert Sutter's former slave, which, if true perpetuates an endless chain of revenge started the moment Robert asked Boy Willie to carve images of the Charleses, Robert's slave family, into the piano he purchased for his wife. The carvings created a feud between the Sutters and the Charleses because both families equally felt the piano belonged to them. In fact, Boy Willie believed the family could not fully be rid of their days as slaves until the Charleses owned the piano rather than the Sutters and stole it, leading to his murder and even to the possible murder of Old Man Sutter, generations later, through the ghost of Boy Willie.
The play is set generations after the days of slavery, and the protagonist, also named Boy Willie after the former slave Boy Wilie, believes the exact opposite of his murdered relative: He believes that if he sells the piano the Charleses stole, he can buy Sutter's land, and being landowners will make the Charleses free of their past as slaves. It is while he is undertaking the task of trying to get his hands on the piano that he sees the ghost of Old Man Sutter playing the piano. Boy Willie and the ghost of Old Man Sutter get into a physical fight, which symbolizes Boy Willie wrestling with his past as a slave, just as Hamlet wrestled with his duty to avenge his father and his conscience. In the end, Boy Willie is triumphant, and the ghost of Sutter is exorcised; however, Boy Willie also decides the piano is far too valuable to the Charles family to sell. Most importantly, he realizes it is his own feelings of dignity and pride that separate him from his past with slavery, not the ownership of either land or a piano.
In the end, Hamlet is released from the past the moment he is finally able to avenge his father by killing his uncle, and Boy Willie is released from his past the moment he realizes his family truly is no longer tied to their days as slaves. In both stories, the appearances of the ghosts help lead to these epiphanies.