Sweet Adelines International competition
The Sweet Adelines International Competitions are the annual global championships for women's barbershop harmony a cappella singing – in quartets and choruses – for members of Sweet Adelines International (SAI) and have been held annually between September and November since 1947. They are now the largest women's singing competition in the world with over 8000 participants at the 2014 convention.
Source: Wikipedia — Sweet Adelines International competition (CC BY-SA 4.0)