descant on(或upon)

• • 详谈，详论，详细论述：

    He descanted endlessly upon the wonders of his trip.

    他没完没了地详述他旅行中所见到的各种奇观。

  • 唱(歌)；奏(乐)[无被动语态]：

    The girl singers were asked to descant on the tune.

    请女歌手们唱这支歌曲。