What can I say about ABBA that hasn't already been said? The combination of Benny Andersson, Frida Lyngstad, Agnetha Fältskog, and Björn Ulvaeus (and, behind the scenes, Michael Tretow) were, for a time in the '70s, an unstoppable juggernaut of disco-infused pop. With some of the most polished productions in music history, ABBA's music has meant different things to each new generation, but it's never gone away. And though their catalogue is rich with gorgeous singles, none captured the public imagination quite like Dancing Queen.