The piece was created for the interactive CD-ROM project `Prisma` dedicated to the music of Saariaho. Listeners could construct their own version of the piece by combining musical fragments separated in the score by double bar lines.
The idea is based on symmetry. Reflections can occur in different dimensions rhythm pitch instrumental gestures or timbre. Saariaho distinguished between `horizontal` mirrors the interaction between flute and cello and `vertical` ones the coincidence of timbres and gestures at a specific moment in time.
In live performance musicians can choose which specific `mirror` connections they want to emphasize making each interpretation unique.