a section; an excerpt If you are referring to the 3 separate parts of a sonata or concerto, we call them "movements". 1st movement; 2nd movement; 3rd movement "A piece of music" refers to the entire piece, not just a part of it.

通常用a piece of music来表示“一段音乐”。 不过a piece of music也有“一首乐曲”的意思，留意一下。

a piece of

demo~~clip~

a part of