Sigur Ròs are playing for four nights at their own Norður Og Niður festival in Iceland at the end of December, and they’ve just announced some additional artists that will be on the bill. (Kevin Shields and Jarvis Cocker are already scheduled to perform.) New acts include Tangerine Dream, GusGus, Kaitlyn Aurelia Smith, and a solo set from the Vaccines’ Árni. In addition, Jónsi has announced that he’ll release a collection of unreleased solo electronic recordings called Frakkur: 2000-2004, which will be available on limited-edition vinyl at the festival. Hear a selection from that below.