> To listen, go to bostonglobe.com/soundtrack. A group of Boston teenagers, a baker’s dozen, crowds into the basement studios of WERS, the Emerson College radio station housed in the Ansin Building on Boston Common. They’re all girls, because, well, that’s the whole point. These are the future voices of GRLZ Radio, a radio station and after-school program run by St. Mary’s Center for Women and Children, in Dorchester’s Uphams Corner. Over 10 years, the girls of GRLZ (streaming at grlzradio.org) have interviewed Governor Deval Patrick, Mayor Tom Menino, and many others, all the while learning radio-production and communication skills. More important, they have gained an outlet for self-expression — an outlet lacking in the poorer neighborhoods where many of the young women live. Now GRLZ Radio is partnering with WERS, providing regular programming for its sister talk-and-information station, ETIN, which streams at etinradio.org. Which is why the aspiring broadcasters are here on a recent weekday receiving training and a pep talk from Howard “D” Simpson, the WERS operations manager. “Nothing is impossible,” he tells them, sharing the story of his own difficult childhood in Boston. Soon the teens will be anchoring newscasts, assembling radio pieces, and handling production duties. It’s their turn at the microphone. They want to be ready.