We have the convention of music of writing this symbol indicating the beat-carrying unit of four so I'm writing a four underneath each of these.

我们有一个约定俗成的书写格式,来表示四拍一单元,所以我在每行这里的下面写上一个四

耶鲁公开课 - 聆听音乐课程节选

Well, in music the most basic symbol for the beat is the quarter note.

音乐中表示拍的最基本符号是四分音符

耶鲁公开课 - 聆听音乐课程节选

That tells a performer that the quarter note is carrying the beat.

这就告诉演奏者,四分音符表示拍

耶鲁公开课 - 聆听音乐课程节选

The quarter note usually carries the beat.

四分音符通常表示拍

耶鲁公开课 - 聆听音乐课程节选