Mamma Mia! is a musical with a book by British playwright Catherine Johnson, based on the songs of ABBA. Björn Ulvaeus and Benny Andersson, who composed the original music for ABBA, have been involved in the development of the show from the beginning. Anni-Frid Lyngstad has been involved financially in the production, while Agnetha Fältskog has not, though she was present at the Swedish premiere and final show. The title of the musical is taken from the group's 1975 chart-topper "Mamma Mia." However, the story has nothing to do with the story of the group; the only link is that Agnetha and Björn and Benny and Anni-Frid became couples in the springtime of 1969, and as the foursome went on vacation to the island of Cyprus the following springtime of 1970, that is also where they performed together for the first time, and thus, ABBA was born.