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."