Berniece is one of the primary characters in The Piano Lesson by August Wilson, and she is the family member who understands the significance of the piano she has in her possession. While it is not exactly a family heirloom, it is certainly symbolic of her family's history. 

Berniece's ancestors, the Charles family, were owned by a plantation owner named Robert Sutter. In 1853, Sutter bought the piano as an anniversary gift for his wife; however, he was forced to use a rather unconventional form of payment, at least by today's standards. He traded two slaves, both members of the Charles family, in order to acquire the instrument.

One of those slaves that was traded was Mama Berniece; the other was Walter, her nine-year-old son. In this exchange, Papa Boy Willie lost his wife and son. To commemorate them, he got permission from Ophelia Sutter to carve their faces into the piano. An expert woodcarver, Papa Boy Willie also carved other scenes into the piano, scenes which depicted the Charles family history.

The Emancipation Proclamation freed the Charles family slaves, but the piano was not emancipated with them. In 1911, members of the Charles family stole the piano. Their rationale was that as long as the piano was owned by the Sutters, the Charles family was still symbolically enslaved to them. Until the piano was free, then, the Charles family would never be free.

There it is. Berniece does not want to let her brother, who has come to claim his half of the piano, sell the piano because it is symbolic of her family's freedom. Her brother, Boy Charles, sees things differently. He wants to sell the piano in order to get the money to buy the Sutter land, something he believes will end, once and for all, the enslavement of the Charles family. 

They each have a valid point, but Berniece's claim to the piano is much stronger than her brother's. To him the piano is a source of revenue; to her it is the thing which most connects her to her family and her heritage. Note the following description of this connection:

When my mama died I shut the top on that piano and I ain't never opened it since. I was only playing it for her. When my daddy died seem like all her life went into that piano. She used to have my playing on it...had Miss Eula come in and teach me...say when I played it she could hear my daddy talking to her. I used to think them pictures came alive and walked through the house. Sometime late at night I could hear my mama talking to them. I said that wasn't gonna happen to me. I don't play that piano cause I don't want to wake them spirits.

While Berniece clearly respects the family legacy of the piano, Boy Charles is seeking his own advancement by buying land and being able to lord it over the white landowners. Her motivation is selfless; his is selfish. She is willing to fight her brother to keep the piano, and it is a fight she deserves to win--and she does.

It takes a supernatural encounter for Boy Charles to understand that this piano is more powerful than he had ever known, and eventually he drops his pursuit of the instrument. The piano stays where it belongs--with Berniece, the only remaining member of the Charles family who understands the symbolic power of the piano.