(Photo credit: Curtis Perry) Baritone Joshua Hopkins and Yannick Nézet-Séguin give the U.S. orchestral premiere of Jake Heggie and Margaret Atwood’s “Songs for Murdered Sisters.” Hopkins’ sister, Nathalie Warmerdam, was one of the victims in one of Canada’s worst cases of domestic violence. Since Warmerdam’s murder in 2015, Hopkins has since set out on a journey to use his voice {…}