A member of the musical group ABBA from Sweden, Björn Kristian Ulvaeus also co-wrote the songs for the musicals Chess, Kristina frn Duvemla, and Mamma Mia! He collaborated on the production of Mamma Mia! The Swedish folk-schlager group Hootenanny Singers, formerly known as the "West Bay Singers," had a huge following in Scandinavia before Ulvaeus rose to fame with ABBA. Here We Go Again with personal friend and fellow ABBA member Benny Andersson. He is the group's senior citizen.