Even the most devoted music aficionado relishes silence every now and then but Sophia gets twitchy.  For instance, she gravitates to opera on the tennis court. She loves its grandeur and oversized scale of emotions. It inspires her to play the net and perfect her blistering serve. Jazz is perfect for kayaking and sandal shopping on Zappos. It’s all about the soundtrack. Yesterday, on the number four train heading uptown to a rooftop Memorial Day barbeque, Sophia’s third iPod of the year broke and she was forced to contend with silence.  She zeroed in on the rhythms around her. Metal clanging against metal as the train rushed through the tunnel. The guy seated across from her tapping out a beat on the nape of his girlfriend’s neck. She tried to be Zen about it and almost succeeded until a young girl with an indy sounding back beat leaking from her headphones sat down next to her. Sophia jumped out at the next stop, hailed a cab and insisted that the driver flood the back seat with whatever he happened to be listening to at the moment. That night, she downloaded four hours of Tuvan throat singers, reliving the river of happiness she floated on during her cab ride uptown.