Power of 12, Nevada County’s homegrown R&B band, will present a 20th anniversary concert in conjunction with the Miners Foundry from 7 to 10 p.m. Sunday. The doors will open at 5:30, and dinner will be available from Anya’s Catering. The Foundry was the site of the band’s first concert in October of 1992, when 16 local musicians came together to play for the benefit of Kent Smith, candidate for the state senate, and the Green Party. Known as The Tribe at first, the band has continued for the next two decades laying down some of the hottest R&B and …