"SOS" was written by Benny Andersson, Björn Ulvaeus and Stig Anderson. The title itself was coined by Stig, though the lyrics he provided were rewritten by Ulvaeus. "SOS" was among the first three songs recorded for the group's upcoming 1975 album, ABBA. Despite the song's catchiness, it was passed over as the lead single from the album; the track "So Long" was chosen instead. "So Long" was chosen primarily because it had the same uptempo beat as their 1974 hit single, "Waterloo." The ...