The polychords in this example are a very distinctive effect. Williams creates an alien/space effect by combining two unrelated chords into a very strange dissonance.

They have to be used with great care as the choice of chords and the way you voice them makes a huge difference. You can see the full voicing and orchestration in the PDF extract at the bottom of this page.

There are two examples in the extract below:

• Bar 62-63: Db major with C major over the top (notice the Db/C and Gb/A clashes but he keeps them far apart in the texture)
• Bar 64: A major with C major over the top (this is a bit more consonant except for the C#/C clashes)
• After the end of the score extract you might also hear a third polychord – C augmented with C over the top