Well, what we now call the black notes-- although historically keyboards could be either way-- you could have these added notes black or white and then these underneath would be black.

我们现在称之为黑色音符,尽管历史上键盘的颜色换成怎样都行,也许增加的音符是白色,而底下的这些音符则是黑色

耶鲁公开课 - 聆听音乐课程节选