For the show, the Somerville Art Matters crew joined local artists and friends at the Somerville Museum, the locale for the event's kick off party that took place April 29. We chat with Mary Curtin, this year's event organizer, who talks about the show's theme: The Green line T that will extend through Somerville. We also talk with artists about the evolution of SOS. What's interesting is that we interview artists who have participated many times, in addition to some newbies for this year. Less