"Whales Tails" captures the alien, ethereal sound that was the Cocteau Twins trademark for the first half of their career (and to a lesser extent for its entirety). Part of its odd beauty can be attributed to the fact that Twins singer Elizabeth Fraser wrote it with nonsense words that had no particular meaning. This was a common practice for her through much of her early work, as she would collect words from books written in languages she didn't' understand. She later abandoned this technique, but spoke about it in an interview with 1FM Radio.
"The music and the singing and the words created the feeling," Fraser said. "I had a freedom doing this that I didn't have singing English... I just didn't have the courage to sing in English. I felt like shark bait. I felt inadequate."
Asked what the nonsense words are in this song, Fraser says they are (something like), "Kim-kim mockalya teluxayomye yak vulla vulla cokala fillame nek," adding that she has no idea what they mean.
Angus Young created the distinctive opening guitar part for "Thuderstruck" by playing with all the strings taped up, except the B. He learned the studio trick from his older brother George Young, who was the rhythm guitarist for The Easybeats.