Depends, I think. Generally, I think accidental copyright infringement by an unsuspecting person who plays the song believing they bought it legally would not be held accountable. But if they knew the song was copyrighted and not legally licensed by the piano manufacturer, and they assembled a bunch of friends to listen to the songs, or resold them for money, then yeah perhaps. Most importantly in context, though, the piano will almost certainly not be fined or taken to court. ;)