‘Bisection’ is a work in three movements for double chamber orchestra. The work uses twin complementary “scales” or hexachords, each of six pitches, which together encompass all twelve pitches available. Each scale has a unique character with its own interval structure and implied harmonies. The work opens with the following hexachords, allocated respectively to Chamber Orchestra A and Chamber Orchestra B:

Scale 1 : C Db E F# G Bb

Scale 2 : D Eb F G# A B

As the work progresses, the scales are transposed from one movement to another while still maintaining their complementary positions. The mix of two common triads and their displacement by a tritone within each scale combines two apparent tonal centres with an inherent tonal contradiction, thereby generating a wide range of harmonic possibilities from the most consonant to the most dissonant.

Conceptually, the two scales can be seen as the musical equivalent of ying/yang – they embrace the complete cosmos of twelve tones but never share the same musical pitches. At various points in the work, the two scales sometimes work together, sometimes in direct opposition and sometimes as echoes of each other, coloured by their different personalities and harmonic character.

To reinforce the separate identities presented by the two scales, the two chamber orchestras feature different woodwind and brass instruments and this extends to the final movement where the marimba and xylophone make their appearance and use two different hexachords.