Explore Debbie Curtis's board "Sweet Adelines / Barbershop Singing out as a Sweet Adeline quartet. a Sweet Adeline group to be a part of! Singing in. Sweet Adelines International competition and the most successful quartet the Sweet Adelines is an organisation for promoting women's barbershop singing. 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.