Links to Barbershop Singing and A Cappella Music Barbershop Harmony SocietyMid-Atlantic District of the Barbershop Harmony SocietySweet Adelines International Greater Nassau ChorusHistory of Barbershop MusicBarbershop Learning Tracks DatabaseResources for SingersBarbershop Hall of FameBarbershops TagsHistory of Acapella MusicAcapella Groups Singing Popular Songs.