It's something like liner notes or a performance history of the cosmos' greatest singing group ever.

就像插画一样,或者是世间最大的合唱队的表演。

耶鲁公开课 - 弥尔顿课程节选

But you can look at manuscripts of the early eleventh century and see people singing Ps and Ls and Os and Ms and things like that.

但是大家可以看看,十一世纪初的手稿,可以看到那时有人在唱P,以及L,O和M之类的

耶鲁公开课 - 聆听音乐课程节选