Väsen is a Sweish folk music band originally consisting of Olov Johansson (nyckelharpa), Mikael Marin (viola) and Roger Tallroth (guitar). Later André Ferrari (percussion) also joined the group. They have released 10 albums, and tour every year also outside of Europe. Since 2002, however, performances outside Sweden have tended to not include André Ferrari, owing to his reluctance to tour internationally and the economic advantage of a trio. Since then, Väsen has released three albums (Trio, Keyed Up, and Live in Tokyo) in this "strings-only" format.