The Dancing Queen Reigns Forever

This summer marks the jubilee of Abba’s eponymous 1975 album. It’s the album that proved the band was not just the one-hit wonder of the Swedish Eurovision winner “Waterloo,” and the songs on it, including “SOS” and “Mamma Mia” (also the name of the musical that returns to Broadway on August 2), made Abba one of the biggest groups in pop history.