Tove reached out through our mutual friend Sophia Wood. The piece played Dona nobis pacem alongside NASA's "Chorus", a VLF recording of electromagnetic waves in the Earth's magnetosphere. Anyone standing outside could sing into their phone and become a voice in the work. Pitch analysis by Mattias Heldner at the Stockholm University Phonetics Laboratory drove particles that formed a pattern across the facade.

I handled the projection mapping, composition and socket data. Sol Sarratea wrote the shaders, David Giese did the video, and Scenteknik ran the rig in Stockholm. Both years we worked out of a freezing cargo container on the square, aligning the mapping as our breath fogged the laptops.

The tricky part was making hundreds of simultaneous voices still feel personal. With anyone in the city able to join from a phone, each singer needed to recognise their own particle, a few pixels moving the way their voice moved. Getting that feeling right is what kept us going in the container.