Most Helpful Girl
Since you both like music assuming because hall are in band, ask her about what intrustment she would like to play besides the one she plays now or what's favorite type of music outside of band? Ask her questions like that or go on about a movie you saw and ask if she saw it and go on commonly like that
Most Helpful Guy
At this point I would say ask her out to do something outside of school. That way you shouldbe able to break through her shyness and get her talking a bit. Once that happens, yyou'll have a better idea of topics. Or just look up random weird facts that could interest her, learn about and bring it up. First idea though, do it.