One of the most successful pop groups of all time, Swedish quartet Abba has sold more than 300 million albums worldwide since their Eurovision debut with Ring, Ring in 1973. The prolific musical partnership of Björn Ulvaeus and Benny Andersson began in 1966 when they co-wrote their first songs. Agnetha Fältskog and Anni-Frid 'Frida' Lyngstad, joined the duo in 1969 and soon the four became romantically involved, with Björn and Agnetha and then Benny and Frida getting married. The group started out providing backing vocals and instrumentation to their respective solo recordings until they began to capitalise on the harmony of their four voices. Their first album Ring, Ring was a success in Sweden but it was their win at the 1974 Eurovision Song Contest with Waterloo that launched their international career. Their third album, 1975’s ABBA featured the smash hit singles, SOS and Mamma Mia. By 1976, the group was a pop sensation and had already released greatest hits compilations in numerous countries, featuring mega-hits such as Dancing Queen and Fernando which sold millions of copies. By the early 80s, Abba’s dynamism was slowing down – both couples had gotten divorced and each member was ready to work on other projects. The announcement in 1982 that the group would take a break signalled the end of Abba, as the potential reunion never came about. However, their music acquired a new life in the 90s all over the world. In 1999, the musical based around their most popular songs Mamma Mia! opened in London’s West End. The musical was huge critical and commercial success and its opening on Broadway two years later was only the first of dozens of international productions, leading to a blockbusting film version in 2008, starring Meryl Streep. In 2010, in honour of their varied and esteemed journey, Abba was inducted into Cleveland, Ohio’s music Museum The Rock And Roll Hall Of Fame.