In the final analysis, there are many different ironies that emerge in Wilson's The Piano Lesson.  I think that one of the most interesting ironies is how a source of historical pain can end up providing a form of restoration. Wilson constructs a drama centered on how individuals understand their pain and hurt in the midst of developing their own identities.  Past, present, and future merge into the mindset of the modern individual.  Berniece represents this in her relationship to the piano:

"Look at this piano. Look at it. Mama Ola polished this piano with her tears for seventeen years. For seventeen years she rubbed on it till her hands bled. Then she rubbed the blood in…mixed it up with the rest of the blood on it. Every day that God breathed life into her body she rubbed and cleaned and polished and prayed over it. ‘Play something for me, Berniece. Play something for me, Berniece.’ Every day… 

It is clear that Berniece looks at the piano as an heirloom of her past.  It is a past carved out of psychological pain and historical suffering.  She doesn't want to open it because of what it represents.  The past for Berniece is to stay in the past.

However, the irony emerges when she has to play the piano in the end of the drama.  She must play it and, in doing so, hurt becomes a point of restoration.  In playing the piano, Berniece has established the irony that what ends up hurting can provide the basis for healing.  If we look at irony as something that seems "deliberately contrary to what one expects," Berniece playing the piano at the end of the drama is one of the most important ironies.  It serves as the basis of how restoration and hope can emerge out of sadness and pain.