Use this Explorer close-up to listen to what's going on in the opening chord of Emerging Dances.
In the opening chord there are five notes, although in this Explorer close-up the two notes played by the oboe and viola can be heard together on one track (the fourth). When they are played together as a chord, these five notes are dissonant (they clash). But if the notes are separated into pairs, particular relationships emerge between the notes.
So the whole chord sounds dissonant because these particular intervals have been mixed together to make up one cluster chord.