High Quality Content by WIKIPEDIA articles! "So Long" is a song by Swedish pop group ABBA, released as the first single from their album ABBA. It was backed with "I've Been Waiting for You". "So Long" was written by Björn Ulvaeus & Benny Andersson, with vocals by Agnetha Fältskog & Anni-Frid Lyngstad. ABBA and their manager, Stig Anderson, decided to release this track instead of the more secure "I've Been Waiting For You" or "S.O.S.", simply because they wanted to show their different styles of music. "So Long" gave ABBA its worst international chart performance, although it was a hit in Sweden, Austria and West Germany. In the UK it failed to chart the TOP 50 reaching 91. It is also notable for the appearance of the refrain from 'Bali Ha'i' during the fade-out.