ZHENG

​Excerpts from “Zheng,” a work in progress by composer Shinji Eshima and librettist Tony Asaro about the life and work of the late mezzo-soprano Zheng Cao, conveyed much of the ferocity and dogged spirit of its subject. Cao, who died of lung cancer in 2013 at 46, was both a gifted artist and an individual of unstoppable personal power, and those qualities came through in the scenes performed Saturday under the baton of conductor Jonathan Khuner. They included duets with her sister and her doctor/fiance, but most tellingly a final stirring paean to the force of her own singing.