I don't know enough about music "layers" or "textures", etc. to say much about that aspect of this wonderful pop song. I know that there's more "going on" (musically, instrumentally) than is initially apparent. The refrain appears to make good use of a Specter-esque "wall of sound" recording technique.

What I really know: Singer Agnetha Fältskog's clear, sweet, plaintive lead vocals vault this song straight to greatness for me.

Not my favorite ABBA song, but it was still a great effort by a fantastic band...

Released on the self-titled full-length ABBA in 1975, S.O.S. was the second big hit for ABBA in the United States (after Waterloo), and the attention was well deserved. Like with most ABBA singles, songwriters Benny Andersson and Björn Ulvaeus hide complexities behind a sugary veneer, resulting in a song enjoyed in one's youth and then rediscovered many years later. The song incorporates tone and pace shifts throughout with an acoustic backdrop for the immortal vocals of Anni-Frid Lyngstad and Agnetha Faltskog. As one of the most popular ABBA numbers, the song has been covered by numerous and diverse artists including Peter Cetera, Celebrity Skin, Meat Purveyors, Radha Kali, Erasure, Javelin Boot, and pretty much every ABBA tribute act at which you can sling a dead cat. S.O.S. charted in the U.S. for 8 weeks in 1975, peaking at #15, and was the only single to chart where both the name and artist are palindromes.