Back in the day: Abba
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Swedish quartet Abba formed in the early 1970s and had a number of minor hits before winning the Eurovision Song Contest in 1974 with Waterloo. The band really took off in the mid-1970s with songs like Dancing Queen and Knowing Me, Knowing You.
Although they've never officially split the foursome haven't gigged together since the early 1980s. One of the most successful acts of all time, they've sold over 270 million records.