Barbership quartet to perform downtown Agate Passage, a barbershop quartet, will sing at 11 a.m. Saturday, June 9 at the plaza next to Blackbird Bakery on Madrone Lane. June 9, 2012 11:30 am Agate Passage, a barbershop quartet, will sing at 11 a.m. Saturday, June 9 at the plaza next to Blackbird Bakery on Madrone Lane. The performance is sponsored by Bainbridge Island Rowing Club.