Macbeth (opera)
In the prelude (the music of the opening) we hear music that comes later in the sleep-walking scene.  The chorus of Witches prophesy the future.  A messenger arrives to say that Macbeth has been given the title and estates of Cawdor.  Macbeth and Banquo, his general, think about the witches’ prophecy.  Half of the prophecy has just come true (the other half being that Macbeth will become king, and that the kings that come after him will be Banquo’s heirs).  The witches dance and sing at the end of this scene.