Cabaret is a forum for the classic American pop song — and the death of singer Mary Cleere Haran, hit by a car coming out of a driveway while she was riding her bike in Deerfield Beach, Fla., robs the world of an activist who interpreted, updated and preserved those brilliant, melodious standards. The genre and milieu in which she worked isn’t my preferred entertainment, but there’s no denying the centrality in sophisticated contemporary culture of the words and music of Rodgers and Hart and Hammerstein, Cole Porter, Frank Loesser, Irving Berlin, George and Ira Gershwin, Jerome Kern, Johnny Mercer and the many others celebrated by Haran, age 58, who wrote and produced shows and contributed significantly to television documentaries about the stars and songs of the U.S. in the mid 20th Century. Though there are performers as devoted to sustaining this legacy of wit and glamor as she, when an artist as deeply into their speciality it taken from the stage in their prime, that specialty is severely wounded, too.