Musician Michael Penn has the enviable, if not incredibly difficult task of scoring “Girls.” OK, that didn’t sound quite right. Allow me to rephrase: Penn composes the music for Lena Dunham’s HBO series, which he’s done from the very beginning. Of course, he’s scored films before -- for Paul Thomas Anderson: “Hard Eight” and “Boogie Nights,” among many other films. I tried to imagine what it must be like to evoke through music the millennial female Brooklyn experience, as a 54-year-old man living in Los Angeles -- and frankly, I couldn’t (and I’m a huge fan of “Girls” and I live in Brooklyn!).