这样大概经过了30秒的样子，就是那个主音和弦。

That held for about thirty seconds, that tonic chord.

youdao

经过多次改造， % 到了元代， 这类乐器基本成熟， 它的主要组成部分是弓和弦。

(v/o) ) After many times of adjustments, this type of musical instruments was quite developed in Yuan Dynasty. It mainly consisted of the bow and the strings.

youdao

That held for about thirty seconds, that tonic chord.

这样大概经过了30秒的样子，就是那个主音和弦。

耶鲁公开课 - 聆听音乐课程节选