Gin my cotton
Sell my seed
Buy my baby
Everything she need
– Skip James
This is a totally fitting epigraph for several reasons. First of all, it's from a song by the famous blues musician Skip James. For more on this highly influential Delta bluesman check out this link. August Wilson often said in interviews that he was highly influenced by the blues. He considered the blues music to be a treasure trove of African-American history and also to be a great form of literature. Given all this, it makes a lot of sense that he would choose lyrics from a blues song for his epigraph.
But why this specific blues song? Well, it seems to us that the lyrics totally sum up Boy Willie's whole plan. He wants to sell the piano so that he can buy land and grow his own cotton. He's sick of working for other people and wants something of his own in the world. Notice that the lyrics repeat the word "my." This parallels Boy Willie's wish to have something that is his. Boy Willie even directly echoes the song in the play. When he first lays out his plan to sell the piano and buy Sutter's land, he says he's going to "Gin my cotton. Get my seed" (1.1.105). We have to wonder if August Wilson might've pulled these lines directly from the Skip James song.
Some have also pointed out that the epigraph might have a hidden meaning. Notice that it includes the line "Buy my baby." This line could be seen as a double entendre, meaning that it has two meanings. You could see the line as meaning that someone is literally buying someone else. This brings to mind the issues of slavery that The Piano Lesson wrestles with throughout. There's nothing to indicate that the original song intended this meaning. It seems like Skip James just wanted to make enough money to buy his lady friend something nice. However, when you think about the lyrics in the context of the play, you could choose to see them in a new light.