law of octaves

例句：

1. 1.The melody is in the keyof C major, which is a perfectoctave.
   这首旋律是C大调，是一个完美的八度。
2. 2. Thepiano player plays an octavehigher than the singer.
   钢琴手演奏的比歌手高一个八度。
3. 3. The orchestraperforms with an octaverange from B flat to G.
   管弦乐队的表演从Bflat到G，跨度为一个八度。