In the harmonic series the prime numbered partials create the octave, the fifth and the third above the fundamental pitch – the building blocks of diatonic harmony. But they also create the so-called conflicting partials – dissonant overtones that create a shimmering aural tension when illuminated against a fundamental pitch. In sudden light I have explored the overtone series as a basis for a large-scale harmonic structure exploiting the diametric nature of consonance and dissonance. I also made use of many sequences of prime numbers in the construction of rhythms, form and some of the smaller musical details.