By Denny Dyroff, Entertainment Editor, The Times Jean Luc Ponty Jean Luc Ponty is one of the most versatile, most progressive and most interesting violinists in today’s music scene – just as he has been for the last 50-plus years. On August 18, Ponty will treat fans with a rare area performance at the Keswick Theater (291 N. Keswick Avenue, Glenside, 215-572-7650, www.keswicktheatre.com). Whether...