All through the early 70's, the foursome work on each others albums. As well as all of them working on Ted Gärdestad's albums and the boys producing other artists. It was a very busy time!

Benny and Björn, along with Michael Tretow were big fans of Phil Spector and his "wall of sound" Once Michael had figured out how it was done, he came up with a similar effect. This involved recording the backtracking several times and putting it together. He also thought it would be nice to see how it would be to put the strings slightly off tune...just for fun. He did the same with the girls voices and thus the "sound of ABBA" was born.