
If you listen to the Waterloo chorus and try to block out the lead melody line, you can hear the Build Me Up melody snippet (sung as Wa - terloo of course!) as the harmony below the lead. When they sing 'Build - me up', the two notes (fourth resolving to third) harmonise with the two notes (sixth resolving to fifth) of 'Wa - terloo'.

(Made in Sweden: Studies in Popular Music - Routledge) It's no surprise that ABBA's early music tends to sound like a deliberate review of what 1960s music had, and I also read Stikkan Anderson tend to buy songs in order to make Swedish hits and make a name for himself and Polar Music before ABBA was formed. The swung notes of "ti, la-la" may be a bit too simple to be merited as a copyrighted melody in my opinion because it's not nearly as complex enough or creative. switching to V-I-V, and then starting the refrain again, discounting the ascending quasi-bluesy diatonic bassline. That Foundations song sounds rather a bit like Baby Love by the Supremes rather than Waterloo, phrasing wise - I suppose I may view it a bit differently because from what I'm picking up there's an I-III-IV-V chord progression in C major for Foundations whereas ABBA's chorus is a rather straight forward I-IV in D major.

There are other claims where Wizzard's See My Baby Jive had a role in inspiring Benny and Björn to make Waterloo, but whichever claim is correct is up to them. I had never heard the claim before, regarding a Tchaikovsky concerto being plagiarised for an ABBA song.
