The Boston Globe's Sam Allis takes a stab at explaining why it's so hard for actors, even those gifted at accents, to nail the Boston accent.
Everyone in movies mangles a Boston accent. It flummoxed Robert Mitchum in "The Friends of Eddie Coyle." Robin Williams's stab at it in "Good Will Hunting" was like fingernails on a blackboard. The Kennedy accents in the movie and television takes about them over the years have been ghastly. Most recently, the stars of "Mystic River" sounded as if they came from five different countries, none of them in this hemisphere.
True 'dat. Sadly, after that promising lede surveying some of the most egregious offenders in the accent rogues' gallery, Allis, too, comes up short of uncovering a definitive answer.
So, what does a Bahstahn accent actually sound like? Those searching for the genuine item should listen to Cambridge's own Lenny Clarke [his frequent pahtnah in crime, Denis Leary, is from Worcester, which doesn't count] or listen to Click and Clack on En-Pee-Ahh.
You may well ask, what about the cinetrix? Does she have an accent? Not online.