"Heirloom" was an existing instrumental track titled "Crabcraft" by electronic musician Console, from his 1998 album "Rocket in the Pocket". Björk contacted Console in early 2000 and they met in London; she then added her vocals on top. "Undo" was written during a two-week session with Knak that January in Reykjavik. Björk recorded her vocals on top of Knak's minimalist rhythmic backbone, and months later she had added a full choir and string section. "Cocoon", also produced by Knak, was one of the last songs to be written for the album; its melody came to Björk in a sudden rush and she contacted him. Knak took it as a chance to make a more minimal track, similar to his own releases. His original treatment of "Cocoon", made with an Ensoniq ASR-10, appeared relatively intact in the final version. Björk also worked with Bogdan Raczynski on the song "Who Is It", but the track did not follow the direction of the record and was subsequently included on the album "Medúlla".