When Amy Tan's novel The Bonesetter's Daughter came out in 2001, a friend, composer Stewart Wallace, presented her with a vocal setting of its opening words. From that seed a full-blown opera has grown, to be given its world premiere at the San Francisco Opera. Working from Tan's libretto — about an American woman who retrieves her Chinese family's past as her mother is slipping into dementia — Wallace evokes the timbres of Chinese opera and uses a cast of mostly Chinese-born singers. Chen Shi-Zheng, who staged the landmark 1999 production of The Peony Pavilion at Lincoln Center, is directing. Says Tan, an operatic neophyte: "I'm hoping the people who otherwise would never go to opera would have a cathartic emotional experience, just as I've had."