A retrospective of performances for the BBC by the biggest acts from around the world. A look at the most memorable songs of ABBA and the music that surrounded them in the 70s.

Perhaps the real mystery is how songs by ... employee. ABBA, of course, had a bubble-gummy, earwormy but complex and distinctive sound that led to an avalanche of ’70s and ’80s hits, ...

But back in 1975, the band nearly gave the song away. ABBA was not at all sure of their future that year. They'd won the Eurovision Song Contest in 1974, and had a hit with the song "Waterloo ...