The piece is written for nine musicians flute percussion harp piano and string quintet and live electronics. The electronics reverb and harmonizer create a kind of `halo` around the instruments expanding their tonal boundaries.
The title and form of the piece are inspired by the Northern Lights in the Arctic sky. Saariaho sought to convey the smooth fluid movements of this natural phenomenon in her music.
This is Saariaho`s first work in which she used computer sound analysis to create instrumental music. The harmonic grid was constructed based on a spectral analysis of cello sounds produced with varying bow pressures.