Sweet Adeline Quartet Champions. they've already achieved major accomplishments as Sweet Adeline barbershop singers. started singing barbershop in the early. So Rare is an award-winning women's a cappella quartet singing smooth sounds and intricate harmonies. No vocal percussion here, just perfectly blended chords in a varied repertoire including swing, jazz, modern and contemporary. To become an active, registered Sweet Adelines Quartet in Australia, you must first register your quartet’s name and members to the International organisation.