Swedish group. Most of the songs were written by Benny Andersson and Björn Ulvaeus, and sometimes Stig Anderson. There have been 7 known masters of the original studio recordings: 1. Original releases (1974–1981) 2. CD releases (1982–1992) 3. ABBA Gold and Thank You for the Music Box Set (1992–1994), remastered by Michael B. Tretow 4. Remastered releases (1997), remastered by Jon Astley and Tim Young. 5. Remastered releases (2001), when Jon Astley revisited his earlier remasters, and fixed some errors. 6. Remastered releases (2005), made by Henrik Jonsson. Featured on “The Complete Studio Recordings” and “The Albums” box sets. 7. Remastered releases (2005–), feature on the Deluxe albums. Some of these albums use the same remasters as the previous two box sets, some are completely new remasters (Voulez-vous, Super Trouper, The Visitors, ABBA).