In Nashville they called her the conscience of country music, but there's no label large enough to encompass Emmylou Harris. Over a career that's lasted nearly 40 years, Emmylou has influenced musical movements from country-rock to the bluegrass revival to Americana, which she helped make into an ongoing genre with her remarkable 1995 album “Wrecking Ball.” In the 1970s and 1980s, Emmylou helped reenergize traditional country music with her crystalline, silvery voice. By now she's something more: a singer who has realized the “Cosmic American Music” that was the dream of her onetime mentor, Gram Parsons. Guitarist and songwriter Buddy Miller, who has backed Emmylou on many occasions and whom she has called one of the best guitar players of all time, opens the program.